diff --git a/sourcepawn/compiler/sc1.c b/sourcepawn/compiler/sc1.c
index ce8f2439d..0b05fdae2 100644
--- a/sourcepawn/compiler/sc1.c
+++ b/sourcepawn/compiler/sc1.c
@@ -3138,6 +3138,13 @@ static void decl_const(int vclass)
   needtoken(tTERM);
 }
 
+static void check_struct_name(const char *name)
+{
+  LayoutSpec spec = deduce_layout_spec_by_name(name);
+  if (!can_redef_layout_spec(spec, Layout_PawnStruct))
+    error(110, name, layout_spec_name(spec));
+}
+
 /*
  * declstruct - declare a struct type
  */
@@ -3148,6 +3155,7 @@ static void declstruct(void)
 	int tok;
 	pstruct_t *pstruct;
 	int size;
+	LayoutSpec spec;
 
 	/* get the explicit tag (required!) */
 	tok = lex(&val,&str);
@@ -3156,10 +3164,7 @@ static void declstruct(void)
 		error(93);
 	}
 
-	if (pstructs_find(str) != NULL)
-	{
-		error(98);
-	}
+	check_struct_name(str);
 
 	pstruct = pstructs_add(str);
 
@@ -3246,8 +3251,9 @@ static void declstruct(void)
  */
 static void domethodmap()
 {
-  int val;
   char *str;
+  LayoutSpec spec;
+  int val, extends;
   char mapname[sNAMEMAX + 1];
   methodmap_t *map;
   methodmap_t *parent = NULL;
@@ -3261,11 +3267,11 @@ static void domethodmap()
   if (!isupper(*mapname))
     error(109, decltype);
 
-  int maptag = pc_addtag(mapname);
-  if (methodmap_find_by_tag(maptag))
-    error(103, decltype, mapname);
+  spec = deduce_layout_spec_by_name(mapname);
+  if (!can_redef_layout_spec(spec, Layout_MethodMap))
+    error(110, mapname, layout_spec_name(spec));
 
-  int extends = matchtoken('<');
+  extends = matchtoken('<');
   if (extends) {
     if (lex(&val, &str) != tSYMBOL) {
       error(93);
@@ -3279,7 +3285,8 @@ static void domethodmap()
 
   map = (methodmap_t *)calloc(1, sizeof(methodmap_t));
   map->parent = parent;
-  map->tag = maptag;
+  map->tag = pc_addtag(mapname);
+  map->spec = Layout_MethodMap;
   strcpy(map->name, mapname);
 
   methodmap_add(map);
@@ -3597,15 +3604,17 @@ static void decl_enum(int vclass)
   cell increment,multiplier;
   constvalue *enumroot;
   symbol *enumsym;
+  LayoutSpec spec;
 
   /* get an explicit tag, if any (we need to remember whether an explicit
    * tag was passed, even if that explicit tag was "_:", so we cannot call
    * pc_addtag() here
    */
   if (lex(&val,&str)==tLABEL) {
-    tag=pc_addtag(str);
-    if (methodmap_find_by_tag(tag))
-      error(110, str, "methodmap");
+    tag = pc_addtag(str);
+    spec = deduce_layout_spec_by_tag(tag);
+    if (!can_redef_layout_spec(spec, Layout_Enum))
+      error(110, str, layout_spec_name(spec));
     explicittag=TRUE;
   } else {
     lexpush();
@@ -3618,11 +3627,13 @@ static void decl_enum(int vclass)
     strcpy(enumname,str);               /* save enum name (last constant) */
     if (!explicittag) {
       tag=pc_addtag(enumname);
-      if (methodmap_find_by_tag(tag))
-        error(110, str, "methodmap");
+      spec = deduce_layout_spec_by_tag(tag);
+      if (!can_redef_layout_spec(spec, Layout_Enum))
+        error(110, enumname, layout_spec_name(spec));
     } else {
-      if (methodmap_find_by_name(enumname))
-        error(110, str, "methodmap");
+      spec = deduce_layout_spec_by_name(enumname);
+      if (!can_redef_layout_spec(spec, Layout_Enum))
+        error(110, enumname, layout_spec_name(spec));
     }
   } else {
     lexpush();                          /* analyze again */
diff --git a/sourcepawn/compiler/sc5.scp b/sourcepawn/compiler/sc5.scp
index bdbefbd20..65e5b743a 100644
--- a/sourcepawn/compiler/sc5.scp
+++ b/sourcepawn/compiler/sc5.scp
@@ -141,12 +141,12 @@ static char *errmsg[] = {
 /*095*/  "cannot have required parameters after optional parameters\n",
 /*096*/  "could not find member \"%s\" in struct \"%s\"\n",
 /*097*/  "symbol \"%s\" does not have a matching type\n",
-/*098*/  "struct requires unique struct name\n",
+/*098*/  "UNUSED\n",
 /*099*/  "member \"%s\" appears more than once in struct \"%s\"\n",
 /*100*/  "function prototypes do not match\n",
 /*101*/  "specify either all dimensions or only the last dimension\n",
 /*102*/  "cannot find %s %s\n",
-/*103*/  "%s %s was already defined\n",
+/*103*/  "UNUSED\n",
 /*104*/  "cannot find any methods for %s\n",
 /*105*/  "cannot find method %s.%s\n",
 /*106*/  "cannot call methods on an array\n",
diff --git a/sourcepawn/compiler/sctracker.c b/sourcepawn/compiler/sctracker.c
index e16c15a24..a4eeba968 100644
--- a/sourcepawn/compiler/sctracker.c
+++ b/sourcepawn/compiler/sctracker.c
@@ -484,3 +484,85 @@ void methodmaps_free()
   methodmap_first = NULL;
   methodmap_last = NULL;
 }
+
+LayoutSpec deduce_layout_spec_by_tag(int tag)
+{
+  symbol *sym;
+  const char *name;
+  methodmap_t *map;
+  if ((map = methodmap_find_by_tag(tag)) != NULL)
+    return map->spec;
+  if (tag & FUNCTAG)
+    return Layout_FuncTag;
+
+  name = pc_tagname(tag);
+  if (pstructs_find(name))
+    return Layout_PawnStruct;
+  if ((sym = findglb(name, sGLOBAL)) != NULL)
+    return Layout_Enum;
+
+  return Layout_None;
+}
+
+LayoutSpec deduce_layout_spec_by_name(const char *name)
+{
+  symbol *sym;
+  methodmap_t *map;
+  int tag = pc_findtag(name);
+  if (tag != -1 && (tag & FUNCTAG))
+    return Layout_FuncTag;
+  if (pstructs_find(name))
+    return Layout_PawnStruct;
+  if ((map = methodmap_find_by_name(name)) != NULL)
+    return map->spec;
+  if ((sym = findglb(name, sGLOBAL)) != NULL)
+    return Layout_Enum;
+
+  return Layout_None;
+}
+
+const char *layout_spec_name(LayoutSpec spec)
+{
+  switch (spec) {
+    case Layout_None:
+      return "<none>";
+    case Layout_Enum:
+      return "enum";
+    case Layout_FuncTag:
+      return "functag";
+    case Layout_PawnStruct:
+      return "deprecated-struct";
+    case Layout_MethodMap:
+      return "methodmap";
+    case Layout_Class:
+      return "class";
+  }
+  return "<unknown>";
+}
+
+int can_redef_layout_spec(LayoutSpec def1, LayoutSpec def2)
+{
+  // Normalize the ordering, since these checks are symmetrical.
+  if (def1 > def2) {
+    LayoutSpec temp = def2;
+    def2 = def1;
+    def1 = temp;
+  }
+
+  switch (def1) {
+    case Layout_None:
+      return TRUE;
+    case Layout_Enum:
+      if (def2 == Layout_Enum || def2 == Layout_FuncTag)
+        return TRUE;
+      return def2 == Layout_MethodMap;
+    case Layout_FuncTag:
+      return def2 == Layout_Enum || def2 == Layout_FuncTag;
+    case Layout_PawnStruct:
+    case Layout_MethodMap:
+      return FALSE;
+    case Layout_Class:
+      return FALSE;
+  }
+  return FALSE;
+}
diff --git a/sourcepawn/compiler/sctracker.h b/sourcepawn/compiler/sctracker.h
index c59d5102d..119269175 100644
--- a/sourcepawn/compiler/sctracker.h
+++ b/sourcepawn/compiler/sctracker.h
@@ -67,6 +67,18 @@ typedef struct pstruct_s
   struct pstruct_s *next;
 } pstruct_t;
 
+// The ordering of these definitions should be preserved for
+// can_redef_layout_spec().
+typedef enum
+{
+  Layout_None,
+  Layout_Enum,
+  Layout_FuncTag,
+  Layout_PawnStruct,
+  Layout_MethodMap,
+  Layout_Class
+} LayoutSpec;
+
 typedef struct methodmap_method_s
 {
   char name[sNAMEMAX+1];
@@ -78,6 +90,7 @@ typedef struct methodmap_s
   struct methodmap_s *next;
   struct methodmap_s *parent;
   int tag;
+  LayoutSpec spec;
   char name[sNAMEMAX+1];
   methodmap_method_t **methods;
   size_t nummethods;
@@ -100,6 +113,14 @@ funcenum_t *funcenums_add(const char *name);
 funcenum_t *funcenums_find_byval(int value);
 functag_t *functags_add(funcenum_t *en, functag_t *src);
 
+/**
+ * Given a name or tag, find any extra weirdness it has associated with it.
+ */
+LayoutSpec deduce_layout_spec_by_tag(int tag);
+LayoutSpec deduce_layout_spec_by_name(const char *name);
+const char *layout_spec_name(LayoutSpec spec);
+int can_redef_layout_spec(LayoutSpec olddef, LayoutSpec newdef);
+
 /**
  * Heap functions
  */
diff --git a/sourcepawn/compiler/tests/fail-redef-methodmap-as-enum.sp b/sourcepawn/compiler/tests/fail-redef-methodmap-as-enum.sp
deleted file mode 100644
index a383a9818..000000000
--- a/sourcepawn/compiler/tests/fail-redef-methodmap-as-enum.sp
+++ /dev/null
@@ -1,15 +0,0 @@
-native CloseHandle(Handle:this);
-
-methodmap Handle {
-	Close = CloseHandle;
-};
-
-methodmap Crab {
-};
-
-enum Crab {
-};
-
-public main()
-{
-}