diff --git a/docs/Errors.txt b/docs/Errors.txt
index 56499b1..f0f0bbc 100644
--- a/docs/Errors.txt
+++ b/docs/Errors.txt
@@ -350,9 +350,14 @@ Operation not supported: Cannot apply "OP" to "TYPE" and "TYPE".
     You tried to use an operator on the wrong type(s) of argument(s),
     like indexing a float or negating a string.
 
-Program counter is unset.
-    You didn't set the program counter, so ACME didn't know where to
-    start.
+Program counter cannot be negative.
+    You used "--setpc VALUE", "* = VALUE" or "!pseudopc VALUE" with a
+    negative number.
+
+Program counter undefined.
+    You tried to generate data before setting the program counter. Use
+    either "--setpc VALUE" on the command line or "* = VALUE" at the
+    start of your source code file.
 
 Quotes still open at end of line.
     You forgot the closing quotes.
@@ -511,6 +516,14 @@ Too deeply nested. Recursive "!source"?
     The default limit is 64, this can be changed using the
     "--maxdepth" CLI switch.
 
+Tried to write to negative address.
+    This means that a new segment inside a !pseudopc block would be
+    placed before the start of the output buffer. Example:
+	* = $1000		; ok (we begin at $1000)
+	!pseudopc $8000 {	; ok (we pretend to be at $8000)
+		* = $5000	; error (we need to go back by $3000,
+	}			; which would mean going to -$2000!)
+
 Unexpected char when evaluating loop condition.
     There was a syntax error while evaluating the loop condition.
 
diff --git a/src/alu.c b/src/alu.c
index 74c4a0f..10c28ec 100644
--- a/src/alu.c
+++ b/src/alu.c
@@ -349,7 +349,7 @@ static void is_not_defined(struct symbol *optional_symbol, char *name, size_t le
 //	FIXME - just split this up into two different buffers, "user name" and "internal name", that way the scope can be changed to a prefix as well!
 // This function is not allowed to change DynaBuf because that's where the
 // symbol name is stored!
-static void get_symbol_value(scope_t scope, size_t name_length, unsigned int unpseudo_count)
+static void get_symbol_value(scope_t scope, size_t name_length, unsigned int unpseudo_count, boolean check_pass_number)
 {
 	struct symbol	*symbol;
 	struct object	*arg;
@@ -365,6 +365,14 @@ static void get_symbol_value(scope_t scope, size_t name_length, unsigned int unp
 	} else {
 		// FIXME - add sanity check for UNDEFINED where EVER_UNDEFINED is false -> BUG()!
 		// (because the only way to have UNDEFINED is the block above, and EVER_UNDEFINED taints everything it touches)
+
+		// special kluge for anonymous backward labels:
+		// if they are referenced before they are defined, the last
+		// value of the previous pass would be used! so we check the
+		// pass number and if the value is from the previous pass, we
+		// delete it:
+		if (check_pass_number && (symbol->pass_number != pass.number))
+			symbol->object.u.number.ntype = NUMTYPE_UNDEFINED;
 	}
 	// first push on arg stack, so we have a local copy we can "unpseudo"
 	arg = &arg_stack[arg_sp++];
@@ -732,7 +740,7 @@ static int parse_octal_or_unpseudo(void)	// now GotByte = '&'
 		if (input_read_scope_and_symbol_name(&scope))	// now GotByte = illegal char
 			return 1;	// error (no string given)
 
-		get_symbol_value(scope, GlobalDynaBuf->size - 1, unpseudo_count);	// -1 to not count terminator
+		get_symbol_value(scope, GlobalDynaBuf->size - 1, unpseudo_count, FALSE);	// -1 to not count terminator, no pass number check
 //	} else if (...) {
 //		// anonymous symbol
 //		"unpseudo"-ing anonymous symbols is not supported
@@ -908,7 +916,7 @@ static boolean expect_argument_or_monadic_operator(struct expression *expression
 		} while (GetByte() == '+');
 		ugly_length_kluge = GlobalDynaBuf->size;	// FIXME - get rid of this!
 		symbol_fix_forward_anon_name(FALSE);	// FALSE: do not increment counter
-		get_symbol_value(section_now->local_scope, ugly_length_kluge, 0);	// no prefix, no unpseudo
+		get_symbol_value(section_now->local_scope, ugly_length_kluge, 0, FALSE);	// no prefix, no unpseudo, no pass number check
 		goto now_expect_dyadic_op;
 
 	case '-':	// NEGATION operator or anonymous backward label
@@ -922,7 +930,7 @@ static boolean expect_argument_or_monadic_operator(struct expression *expression
 		SKIPSPACE();
 		if (BYTE_FOLLOWS_ANON(GotByte)) {
 			dynabuf_append(GlobalDynaBuf, '\0');
-			get_symbol_value(section_now->local_scope, GlobalDynaBuf->size - 1, 0);	// no prefix, -1 to not count terminator, no unpseudo
+			get_symbol_value(section_now->local_scope, GlobalDynaBuf->size - 1, 0, TRUE);	// no prefix, -1 to not count terminator, no unpseudo, check pass number
 			goto now_expect_dyadic_op;
 		}
 
@@ -1008,7 +1016,7 @@ static boolean expect_argument_or_monadic_operator(struct expression *expression
 
 		// here we need to put '.' into GlobalDynaBuf even though we have already skipped it:
 		if (input_read_scope_and_symbol_name_KLUGED(&scope) == 0) {	// now GotByte = illegal char
-			get_symbol_value(scope, GlobalDynaBuf->size - 1, 0);	// -1 to not count terminator, no unpseudo
+			get_symbol_value(scope, GlobalDynaBuf->size - 1, 0, FALSE);	// -1 to not count terminator, no unpseudo, no pass number check
 			goto now_expect_dyadic_op;	// ok
 		}
 
@@ -1018,7 +1026,7 @@ static boolean expect_argument_or_monadic_operator(struct expression *expression
 	case CHEAP_PREFIX:	// cheap local symbol
 		//printf("looking in cheap scope %d\n", section_now->cheap_scope);
 		if (input_read_scope_and_symbol_name(&scope) == 0) {	// now GotByte = illegal char
-			get_symbol_value(scope, GlobalDynaBuf->size - 1, 0);	// -1 to not count terminator, no unpseudo
+			get_symbol_value(scope, GlobalDynaBuf->size - 1, 0, FALSE);	// -1 to not count terminator, no unpseudo, no pass number check
 			goto now_expect_dyadic_op;	// ok
 		}
 
@@ -1058,7 +1066,7 @@ static boolean expect_argument_or_monadic_operator(struct expression *expression
 // however, apart from that check above, function calls have nothing to do with
 // parentheses: "sin(x+y)" gets parsed just like "not(x+y)".
 				} else {
-					get_symbol_value(SCOPE_GLOBAL, GlobalDynaBuf->size - 1, 0);	// no prefix, -1 to not count terminator, no unpseudo
+					get_symbol_value(SCOPE_GLOBAL, GlobalDynaBuf->size - 1, 0, FALSE);	// no prefix, -1 to not count terminator, no unpseudo, no pass number check
 					goto now_expect_dyadic_op;
 				}
 			}
diff --git a/src/output.c b/src/output.c
index d2df681..664c54d 100644
--- a/src/output.c
+++ b/src/output.c
@@ -411,7 +411,7 @@ static void start_segment(intval_t address_change, bits segment_flags)
 	// calculate start of new segment
 	out->write_idx = out->write_idx + address_change;
 	if (out->write_idx < 0) {
-		throw_serious_error("Tried to write to negative addresses.");
+		throw_serious_error("Tried to write to negative address.");
 	} else if (out->write_idx >= OUTBUF_MAXSIZE) {
 		throw_serious_error("Reached memory limit.");
 	}
diff --git a/src/version.h b/src/version.h
index 4d5ed85..bbfb165 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	"14 Aug"	// update before release	FIXME
+#define CHANGE_DATE	"15 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/negativeaddress.a b/testing/errors/negativeaddress.a
new file mode 100644
index 0000000..cdc8555
--- /dev/null
+++ b/testing/errors/negativeaddress.a
@@ -0,0 +1,5 @@
+	*=$1000
+	!pseudopc $8000 {
+		* = $6000	; -> "Tried to write to negative address."
+		rts
+	}
diff --git a/testing/errors/valuenotdefined6.a b/testing/errors/valuenotdefined6.a
new file mode 100644
index 0000000..b36dfe9
--- /dev/null
+++ b/testing/errors/valuenotdefined6.a
@@ -0,0 +1,4 @@
+	*=$1000
+	jmp --	; -> "Symbol not defined."
+-- ; older versions had a bug where the last value set in a pass survived to the next pass
+	jmp --