diff --git a/asm/pptok.pl b/asm/pptok.pl
index 0ba6bed6..0b8ef251 100755
--- a/asm/pptok.pl
+++ b/asm/pptok.pl
@@ -1,7 +1,7 @@
 #!/usr/bin/perl
 ## --------------------------------------------------------------------------
 ##
-##   Copyright 1996-2020 The NASM Authors - All Rights Reserved
+##   Copyright 1996-2022 The NASM Authors - All Rights Reserved
 ##   See the file AUTHORS included with the NASM distribution for
 ##   the specific copyright holders.
 ##
@@ -132,7 +132,8 @@ if ($what eq 'h') {
 	}
 	$n++;
     }
-    printf OUT "    %-24s = %3d\n", 'PP_INVALID', -1;
+    printf OUT "    %-24s = %3d,\n", 'PP_count', $n;
+    printf OUT "    %-24s = %3d\n", 'PP_invalid', -1;
     print OUT "};\n";
     print OUT "\n";
 
@@ -257,11 +258,11 @@ if ($what eq 'c') {
     print  OUT "\n";
     print  OUT "    ix = hashdata[k1] + hashdata[k2];\n";
     printf OUT "    if (ix >= %d)\n", scalar(@pptok);
-    print OUT  "        return PP_INVALID;\n";
+    print OUT  "        return PP_invalid;\n";
     print OUT  "\n";
 
     print OUT  "    if (!pp_directives[ix] || nasm_stricmp(pp_directives[ix], token))\n";
-    print OUT  "        return PP_INVALID;\n";
+    print OUT  "        return PP_invalid;\n";
     print OUT  "\n";
     print OUT  "    return ix;\n";
     print OUT  "}\n";
@@ -315,11 +316,11 @@ if ($what eq 'c') {
     # Comparing to pptok here is correct, because this hash produces
     # an enum preproc_token value directly.
     printf OUT "    if (ix >= %d)\n", scalar(@pptok);
-    print OUT  "        return PP_INVALID;\n";
+    print OUT  "        return PP_invalid;\n";
     print OUT  "\n";
 
     print OUT  "    if (!pp_directives[ix] || nasm_stricmp(pp_directives[ix]+1, token))\n";
-    print OUT  "        return PP_INVALID;\n";
+    print OUT  "        return PP_invalid;\n";
     print OUT  "\n";
     print OUT  "    return ix;\n";
     print OUT  "}\n";
diff --git a/asm/preproc.c b/asm/preproc.c
index 64ba4e71..691f1d97 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -111,6 +111,13 @@ typedef struct Line Line;
 typedef struct Include Include;
 typedef struct Cond Cond;
 
+/*
+ * Map of preprocessor directives that are also preprocessor functions;
+ * if they are at the beginning of a line they are a function if and
+ * only if they are followed by a (
+ */
+static bool pp_op_may_be_function[PP_count];
+
 /*
  * This is the internal form which we break input lines up into.
  * Typically stored in linked lists.
@@ -3757,7 +3764,7 @@ static int do_directive(Token *tline, Token **output)
     }
 
     switch (op) {
-    case PP_INVALID:
+    case PP_invalid:
         return NO_DIRECTIVE_FOUND;
 
     case PP_LINE:
@@ -3828,6 +3835,11 @@ static int do_directive(Token *tline, Token **output)
         }
     }
 
+    if (pp_op_may_be_function[op]) {
+        if (tok_is(skip_white(tline->next), '('))
+            return NO_DIRECTIVE_FOUND; /* Expand as a preprocessor function */
+    }
+
     switch (op) {
     default:
         nasm_nonfatal("unknown preprocessor directive `%s'", dname);
@@ -7001,6 +7013,11 @@ static void pp_add_magic_stdmac(void)
             }
         }
         define_smacro(m->name, m->casesense, NULL, &tmpl);
+        if (m->name[0] == '%') {
+            enum preproc_token op = pp_token_hash(m->name);
+            if (op != PP_invalid)
+                pp_op_may_be_function[op] = true;
+        }
     }
 
     /* %is...() macro functions */