diff --git a/src/asm/globlex.c b/src/asm/globlex.c
index 17032553..14f45c5d 100644
--- a/src/asm/globlex.c
+++ b/src/asm/globlex.c
@@ -198,10 +198,10 @@ char *AppendMacroArg(char whichArg, char *dest, size_t *destIndex)
 
 	if (whichArg == '@')
 		marg = sym_FindMacroArg(-1);
-	else if (whichArg >= '0' && whichArg <= '9')
+	else if (whichArg >= '1' && whichArg <= '9')
 		marg = sym_FindMacroArg(whichArg - '0');
 	else
-		fatalerror("Malformed ID");
+		fatalerror("Invalid macro argument '\\%c' in symbol", whichArg);
 
 	if (!marg)
 		fatalerror("Macro argument '\\%c' not defined", whichArg);
diff --git a/test/asm/symbol-invalid-macro-arg.asm b/test/asm/symbol-invalid-macro-arg.asm
new file mode 100644
index 00000000..6806b7e3
--- /dev/null
+++ b/test/asm/symbol-invalid-macro-arg.asm
@@ -0,0 +1 @@
+x\0
diff --git a/test/asm/symbol-invalid-macro-arg.out b/test/asm/symbol-invalid-macro-arg.out
new file mode 100644
index 00000000..ff94c3c2
--- /dev/null
+++ b/test/asm/symbol-invalid-macro-arg.out
@@ -0,0 +1,2 @@
+ERROR: symbol-invalid-macro-arg.asm(1):
+    Invalid macro argument '\0' in symbol