diff --git a/sdk/tools/spec2def/spec2def.c b/sdk/tools/spec2def/spec2def.c
index 324f88405fd..b929487069d 100644
--- a/sdk/tools/spec2def/spec2def.c
+++ b/sdk/tools/spec2def/spec2def.c
@@ -732,7 +732,8 @@ OutputLine_def(FILE *fileDest, EXPORT *pexp)
     else
         OutputLine_def_GCC(fileDest, pexp);
 
-    if (pexp->uFlags & FL_ORDINAL)
+    /* On GCC builds we force ordinals */
+    if ((pexp->uFlags & FL_ORDINAL) || (!gbMSComp && !gbImportLib))
     {
         fprintf(fileDest, " @%d", pexp->nOrdinal);
     }
@@ -772,7 +773,7 @@ Fatalv(
 
     /* Get the length of the line */
     pcLineEnd = strpbrk(pcLine, "\r\n");
-    len = pcLineEnd - pcLine;
+    len = (unsigned)(pcLineEnd - pcLine);
 
     if (pc == NULL)
     {
@@ -1299,6 +1300,52 @@ ParseFile(char* pcStart, FILE *fileDest, unsigned *cExports)
     return pexports;
 }
 
+int
+ApplyOrdinals(EXPORT* pexports, unsigned cExports)
+{
+    unsigned short i, j;
+    char* used;
+
+    /* Allocate a table to mark used ordinals */
+    used = malloc(65536);
+    if (used == NULL)
+    {
+        fprintf(stderr, "Failed to allocate memory for ordinal use table\n");
+        return -1;
+    }
+    memset(used, 0, 65536);
+
+    /* Pass 1: mark the ordinals that are already used */
+    for (i = 0; i < cExports; i++)
+    {
+        if (pexports[i].uFlags & FL_ORDINAL)
+        {
+            if (used[pexports[i].nOrdinal] != 0)
+            {
+                fprintf(stderr, "Found duplicate ordinal: %u\n", pexports[i].nOrdinal);
+                return -1;
+            }
+            used[pexports[i].nOrdinal] = 1;
+        }
+    }
+
+    /* Pass 2: apply available ordinals */
+    for (i = 0, j = 1; i < cExports; i++)
+    {
+        if ((pexports[i].uFlags & FL_ORDINAL) == 0)
+        {
+            while (used[j] != 0)
+                j++;
+
+            pexports[i].nOrdinal = j;
+            used[j] = 1;
+        }
+    }
+
+    free(used);
+    return 0;
+}
+
 void usage(void)
 {
     printf("syntax: spec2def [<options> ...] <spec file>\n"
@@ -1465,10 +1512,19 @@ int main(int argc, char *argv[])
     pexports = ParseFile(pszSource, file, &cExports);
     if (pexports == NULL)
     {
-        fprintf(stderr, "Failed to allocate memory for export data!\n");
+        fprintf(stderr, "error: could not parse file!\n");
         return -1;
     }
 
+    if (!gbMSComp)
+    {
+        if (ApplyOrdinals(pexports, cExports) < 0)
+        {
+            fprintf(stderr, "error: could not apply ordinals!\n");
+            return -1;
+        }
+    }
+
     if (pszDefFileName)
     {
         /* Open output file */