diff --git a/src/main/java/dk/camelot64/kickc/Compiler.java b/src/main/java/dk/camelot64/kickc/Compiler.java
index 007887de0..7357dface 100644
--- a/src/main/java/dk/camelot64/kickc/Compiler.java
+++ b/src/main/java/dk/camelot64/kickc/Compiler.java
@@ -164,7 +164,6 @@ public class Compiler {
          }
 
          Pass0GenerateStatementSequence pass0GenerateStatementSequence = new Pass0GenerateStatementSequence(cParser, cFileContext, program, variableBuilderConfig, callingConvention);
-
          pass0GenerateStatementSequence.generate();
 
          StatementSequence sequence = program.getStatementSequence();
@@ -199,6 +198,7 @@ public class Compiler {
 
       new Pass1GenerateControlFlowGraph(program).execute();
       new Pass1ResolveForwardReferences(program).execute();
+      new Pass1AssertProcedureDefined(program).execute();
       new PassNAssertStructMembers(program).execute();
       new Pass1UnwindBlockScopes(program).execute();
       new Pass1Procedures(program).execute();
diff --git a/src/main/java/dk/camelot64/kickc/passes/Pass0GenerateStatementSequence.java b/src/main/java/dk/camelot64/kickc/passes/Pass0GenerateStatementSequence.java
index 842612738..59ccb37a9 100644
--- a/src/main/java/dk/camelot64/kickc/passes/Pass0GenerateStatementSequence.java
+++ b/src/main/java/dk/camelot64/kickc/passes/Pass0GenerateStatementSequence.java
@@ -245,7 +245,7 @@ public class Pass0GenerateStatementSequence extends KickCParserBaseVisitor<Objec
       if(existingSymbol!=null) {
          // Already declared  - check equality
          if(!SymbolTypeConversion.procedureDeclarationMatch((Procedure) existingSymbol, procedure))
-            throw new CompileError("Error! Conflicting declarations for "+procedure.getFullName(), StatementSource.procedureBegin(ctx));
+            throw new CompileError("Error! Conflicting declarations for: "+procedure.getFullName(), StatementSource.procedureBegin(ctx));
       } else {
          // Not declared before - add it
          program.getScope().add(procedure);
@@ -261,7 +261,7 @@ public class Pass0GenerateStatementSequence extends KickCParserBaseVisitor<Objec
          // Check that the body has not already been added
          for(Statement statement : sequence.getStatements())
             if(statement instanceof StatementProcedureBegin && ((StatementProcedureBegin) statement).getProcedure().equals(procedure.getRef()))
-               throw new CompileError("Error! Redefinition of function "+procedure.getFullName(), StatementSource.procedureBegin(ctx));
+               throw new CompileError("Error! Redefinition of function: "+procedure.getFullName(), StatementSource.procedureBegin(ctx));
          // Add the body
          scopeStack.push(procedure);
          sequence.addStatement(new StatementProcedureBegin(procedure.getRef(), StatementSource.procedureBegin(ctx), Comment.NO_COMMENTS));
diff --git a/src/main/java/dk/camelot64/kickc/passes/Pass1AssertProcedureDefined.java b/src/main/java/dk/camelot64/kickc/passes/Pass1AssertProcedureDefined.java
new file mode 100644
index 000000000..96a69692d
--- /dev/null
+++ b/src/main/java/dk/camelot64/kickc/passes/Pass1AssertProcedureDefined.java
@@ -0,0 +1,30 @@
+package dk.camelot64.kickc.passes;
+
+import dk.camelot64.kickc.model.CompileError;
+import dk.camelot64.kickc.model.ControlFlowBlock;
+import dk.camelot64.kickc.model.Program;
+import dk.camelot64.kickc.model.symbols.Label;
+import dk.camelot64.kickc.model.symbols.Procedure;
+
+import java.util.Collection;
+
+/** Pass that checks that all functions declared have a definition with a body*/
+public class Pass1AssertProcedureDefined extends Pass1Base {
+
+   public Pass1AssertProcedureDefined(Program program) {
+      super(program);
+   }
+
+   @Override
+   public boolean step() {
+      final Collection<Procedure> allProcedures = getScope().getAllProcedures(true);
+      for(Procedure procedure : allProcedures) {
+         final Label procedureLabel = procedure.getLabel();
+         final ControlFlowBlock procedureBlock = getGraph().getBlock(procedureLabel.getRef());
+         if(procedureBlock == null)
+            throw new CompileError("Error! Function is never declared: " + procedure.getFullName());
+      }
+      return false;
+   }
+
+}
diff --git a/src/test/java/dk/camelot64/kickc/test/TestPrograms.java b/src/test/java/dk/camelot64/kickc/test/TestPrograms.java
index 77d68f409..f63f1065c 100644
--- a/src/test/java/dk/camelot64/kickc/test/TestPrograms.java
+++ b/src/test/java/dk/camelot64/kickc/test/TestPrograms.java
@@ -37,14 +37,19 @@ public class TestPrograms {
    public TestPrograms() {
    }
 
+   @Test
+   public void testCStyleDeclMissing() throws IOException, URISyntaxException {
+      assertError("cstyle-decl-missing", "Error! Function is never declared: sum");
+   }
+
    @Test
    public void testCStyleDeclRedefinition() throws IOException, URISyntaxException {
-      assertError("cstyle-decl-redefinition", "Error! Redefinition of function sum");
+      assertError("cstyle-decl-redefinition", "Error! Redefinition of function: sum");
    }
 
    @Test
    public void testCStyleDeclMismatch() throws IOException, URISyntaxException {
-      assertError("cstyle-decl-mismatch", "Error! Conflicting declarations for sum");
+      assertError("cstyle-decl-mismatch", "Error! Conflicting declarations for: sum");
    }
 
    @Test
diff --git a/src/test/kc/cstyle-decl-missing.kc b/src/test/kc/cstyle-decl-missing.kc
new file mode 100644
index 000000000..969b98867
--- /dev/null
+++ b/src/test/kc/cstyle-decl-missing.kc
@@ -0,0 +1,18 @@
+// Test function declarations
+// Definition of function missing
+
+// Declaration of a sum-function
+char sum(char a, int b);
+
+char * const SCREEN = 0x0400;
+
+// Definition of main()
+void main() {
+    SCREEN[0] = sum('a', 2);
+    SCREEN[1] = sum('a', 12);
+}
+
+
+
+
+