diff --git a/src/acme.c b/src/acme.c
index 46de09e..04cb0a7 100644
--- a/src/acme.c
+++ b/src/acme.c
@@ -399,9 +399,9 @@ static void perform_pass(bits passflags)
 	}
 	// now increment pass number
 	// this must be done _after_ the pass because assignments done via
-	// "-DSYMBOL=VALUE" cli args must be handled as if they were done at the
-	// start of pass 1, so we cannot change that variable at the start of
-	// the pass.
+	// "-D SYMBOL=VALUE" cli args must be handled as if they were done at
+	// the start of pass 1, so we cannot change that variable at the start
+	// of the pass.
 	++pass.number;
 }
 
@@ -788,7 +788,7 @@ int main(int argc, const char *argv[])
 	if (argc == 1)
 		show_help_and_exit();
 	cliargs_init(argc, argv);
-	// init pass number because any assignments done via "-DSYMBOL=VALUE"
+	// init pass number because any assignments done via "-D SYMBOL=VALUE"
 	// cli args must be handled as if they happened at the start of pass 1:
 	pass.number = 1;
 	// init platform-specific stuff.
diff --git a/src/alu.c b/src/alu.c
index 820cac6..aa061d4 100644
--- a/src/alu.c
+++ b/src/alu.c
@@ -1405,7 +1405,7 @@ static boolean string_differs(const struct object *self, const struct object *ot
 
 // int/float:
 // assign new value
-static void number_assign(struct object *self, const struct object *new_value, boolean accept_change)
+static boolean number_assign(struct object *self, const struct object *new_value, boolean accept_change)
 {
 	bits	own_flags	= self->u.number.flags,
 		other_flags	= new_value->u.number.flags;
@@ -1427,10 +1427,9 @@ static void number_assign(struct object *self, const struct object *new_value, b
 	} else {
 		// symbol is already defined, so compare new and old values
 		// if values differ, complain and return
-		if (number_differs(self, new_value)) {
-			throw_error(exception_symbol_defined);
-			return;
-		}
+		if (number_differs(self, new_value))
+			return TRUE;	// -> throw "symbol already defined" error
+
 		// values are the same, so only fiddle with flags
 	}
 
@@ -1448,29 +1447,30 @@ static void number_assign(struct object *self, const struct object *new_value, b
 	own_flags |= other_flags & (NUMBER_FITS_BYTE | NUMBER_EVER_UNDEFINED);
 
 	self->u.number.flags = own_flags;
+	return FALSE;
 }
 
 
 // list:
 // assign new value
-static void list_assign(struct object *self, const struct object *new_value, boolean accept_change)
+static boolean list_assign(struct object *self, const struct object *new_value, boolean accept_change)
 {
-	if ((!accept_change) && list_differs(self, new_value)) {
-		throw_error(exception_symbol_defined);
-		return;
-	}
+	if ((!accept_change) && list_differs(self, new_value))
+		return TRUE;	// -> throw "symbol already defined" error
+
 	*self = *new_value;
+	return FALSE;
 }
 
 // string:
 // assign new value
-static void string_assign(struct object *self, const struct object *new_value, boolean accept_change)
+static boolean string_assign(struct object *self, const struct object *new_value, boolean accept_change)
 {
-	if ((!accept_change) && string_differs(self, new_value)) {
-		throw_error(exception_symbol_defined);
-		return;
-	}
+	if ((!accept_change) && string_differs(self, new_value))
+		return TRUE;	// -> throw "symbol already defined" error
+
 	*self = *new_value;
+	return FALSE;
 }
 
 
diff --git a/src/alu.h b/src/alu.h
index 0f861aa..9d95fa9 100644
--- a/src/alu.h
+++ b/src/alu.h
@@ -16,7 +16,7 @@ struct type {
 	const char	*name;
 	boolean		(*is_defined)(const struct object *self);
 	boolean		(*differs)(const struct object *self, const struct object *other);
-	void		(*assign)(struct object *self, const struct object *new_value, boolean accept_change);
+	boolean		(*assign)(struct object *self, const struct object *new_value, boolean accept_change);
 	void		(*monadic_op)(struct object *self, const struct op *op);
 	void		(*dyadic_op)(struct object *self, const struct op *op, struct object *other);
 	void		(*fix_result)(struct object *self);
diff --git a/src/config.h b/src/config.h
index 85628c8..24649f4 100644
--- a/src/config.h
+++ b/src/config.h
@@ -22,7 +22,7 @@ typedef signed int	intval_t;	// at least 32 bits
 typedef unsigned int	uintval_t;	// at least 32 bits (only used for logical shift right)
 #define OUTBUF_MAXSIZE	0x1000000	// 16 MiB ought to be enough for anybody
 
-// struct to remember where macros were defined (FIXME - use for symbols as well!)
+// struct to remember where macros/symbols were defined
 struct location {
 	const char	*plat_filename;	// filename in platform style
 	int		line_number;
diff --git a/src/global.c b/src/global.c
index 3b23495..4c7a291 100644
--- a/src/global.c
+++ b/src/global.c
@@ -627,12 +627,19 @@ void throw_redef_error(const char error_msg[], struct location *old_def, const c
 	// show error with current location
 	throw_error(error_msg);
 
+	// symbol structs do not necessarily have valid location data:
+	if (old_def->plat_filename == NULL)
+		return;
+
 	// CAUTION, ugly kluge: fiddle with section_now data to generate
 	// "earlier definition" section.
 	// buffer old section
 	buffered_section_type = section_now->type;
 	buffered_section_title = section_now->title;
 	// set new (fake) section
+	// FIXME - maybe store section in definition, just as location is stored?
+	// then we could use real data here instead of faking it, but it would
+	// take a bit more memory...
 	section_now->type = "earlier";
 	section_now->title = "section";
 	// show info message with location of earlier definition
diff --git a/src/symbol.c b/src/symbol.c
index 78f7b3a..91950d4 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -123,6 +123,10 @@ struct symbol *symbol_find(scope_t scope)
 		symbol->has_been_read = FALSE;
 		symbol->has_been_reported = FALSE;
 		symbol->pseudopc = NULL;
+		// we must set "definition" fields to dummy data, because the object
+		// has been created, but not necessarily set to a defined value:
+		symbol->definition.plat_filename = NULL;
+		symbol->definition.line_number = 0;
 	} else {
 		symbol = node->body;
 	}
@@ -142,6 +146,8 @@ struct symbol *symbol_find(scope_t scope)
 //	CAUTION: actual incrementing of counter is then done directly without calls here!
 void symbol_set_object(struct symbol *symbol, struct object *new_value, bits powers)
 {
+	boolean	complain;
+
 	if (symbol->object.type == NULL) {
 		// symbol has no object assigned to it yet
 		symbol->object = *new_value;	// copy whole struct including type
@@ -154,22 +160,27 @@ void symbol_set_object(struct symbol *symbol, struct object *new_value, bits pow
 		// if too different, needs power (or complains)
 		if (symbol->object.type != new_value->type) {
 			if (!(powers & POWER_CHANGE_OBJTYPE))
-				throw_error(exception_symbol_defined);
-			// CAUTION: if above line throws error, we still go ahead and change type!
+				complain = TRUE;
+			// CAUTION: if line above triggers, we still go ahead and change type!
 			// this is to keep "!for" working, where the counter var is accessed.
 			symbol->object = *new_value;	// copy whole struct including type
 			// clear flag so caller can adjust force bits:
 			symbol->has_been_read = FALSE;	// it's basically a new symbol now
 		} else {
 			// symbol and new value have compatible types, so call handler:
-			symbol->object.type->assign(&symbol->object, new_value, !!(powers & POWER_CHANGE_VALUE));
+			complain = symbol->object.type->assign(&symbol->object, new_value, !!(powers & POWER_CHANGE_VALUE));
 		}
+		// if needed, throw "already defined" error with location of previous definition
+		if (complain)
+			throw_redef_error(exception_symbol_defined, &symbol->definition, "Previous definition.");
 	}
 	// if symbol is an address, give it a pseudopc context:
 	if ((symbol->object.type == &type_number)
 	&& (symbol->object.u.number.addr_refs == 1)) {
 		symbol->pseudopc = pseudopc_get_context();
 	}
+	// remember current location for "symbol twice" errors in future:
+	input_get_location(&symbol->definition);
 }
 
 
@@ -212,6 +223,8 @@ void symbol_define(intval_t value)
 	result.u.number.val.intval = value;
 	symbol = symbol_find(SCOPE_GLOBAL);
 	symbol->object = result;
+	symbol->definition.plat_filename = "\"-D SYMBOL=VALUE\"";
+	symbol->definition.line_number = 1;
 }
 
 
diff --git a/src/symbol.h b/src/symbol.h
index a5ec826..0829e4c 100644
--- a/src/symbol.h
+++ b/src/symbol.h
@@ -17,7 +17,7 @@ struct symbol {
 	boolean		has_been_read;	// to find out if actually used
 	boolean		has_been_reported;	// indicates "has been reported as undefined"
 	struct pseudopc	*pseudopc;	// for "unpseudopc"-Operator '&', may be NULL
-//TODO	struct location	definition;	// for "label twice" error
+	struct location	definition;	// for "label twice" error
 };
 
 
diff --git a/src/version.h b/src/version.h
index 7f06a18..83a44ef 100644
--- a/src/version.h
+++ b/src/version.h
@@ -9,7 +9,7 @@
 
 #define RELEASE		"0.97"		// update before release	FIXME
 #define CODENAME	"Zem"		// update before release
-#define CHANGE_DATE	"8 Aug"	// update before release	FIXME
+#define CHANGE_DATE	"9 Aug"	// update before release	FIXME
 #define CHANGE_YEAR	"2024"		// update before release
 //#define HOME_PAGE	"http://home.pages.de/~mac_bacon/smorbrod/acme/"
 #define HOME_PAGE	"http://sourceforge.net/p/acme-crossass/"	// FIXME
diff --git a/testing/errors/Makefile b/testing/errors/Makefile
index e957db9..9951226 100644
--- a/testing/errors/Makefile
+++ b/testing/errors/Makefile
@@ -1,4 +1,4 @@
-ACMEFLAGS	= -v0
+ACMEFLAGS	= -v0 --color
 FILES	:= $(wildcard *.a)
 TESTS	= $(subst .a,.test,$(FILES))
 
diff --git a/testing/warnings/Makefile b/testing/warnings/Makefile
index 6696a06..c245de1 100644
--- a/testing/warnings/Makefile
+++ b/testing/warnings/Makefile
@@ -1,4 +1,4 @@
-ACMEFLAGS	= -v0
+ACMEFLAGS	= -v0 --color
 FILES		:= $(wildcard *.a)
 FAILTESTS	= $(subst .a,.fail,$(FILES))
 SUCCTESTS	= $(subst .a,.succ,$(FILES))