diff --git a/c_gen/c_match.py b/c_gen/c_match.py
index 53cd944..b5ef80a 100644
--- a/c_gen/c_match.py
+++ b/c_gen/c_match.py
@@ -177,27 +177,19 @@
     of_match_fields_t masks;
 } of_match_t;
 
-/**
- * Mask the values in the match structure according to its fields
+/*
+ * AND 'len' bytes starting from 'value' with the corresponding byte in
+ * 'mask'.
  */
-static inline void of_match_values_mask(of_match_t *match)
-{
-    int idx;
-
-    for (idx = 0; idx < sizeof(of_match_fields_t); idx++) {
-        ((uint8_t *)&match->fields)[idx] &= ((uint8_t *)&match->masks)[idx];
-    }
-}
-
 static inline void
-of_memmask(void *_fields, void *_masks, size_t len)
+of_memmask(void *value, const void *mask, size_t len)
 {
-    int idx;
-    uint8_t *fields = _fields;
-    uint8_t *masks = _masks;
+    int i;
+    uint8_t *v = value;
+    const uint8_t *m = mask;
 
-    for (idx = 0; idx < len; idx++) {
-        fields[idx] &= masks[idx];
+    for (i = 0; i < len; i++) {
+        v[i] &= m[i];
     }
 }
 
diff --git a/c_gen/c_test_gen.py b/c_gen/c_test_gen.py
index 01f1c5d..6cc9612 100644
--- a/c_gen/c_test_gen.py
+++ b/c_gen/c_test_gen.py
@@ -272,7 +272,7 @@
     }
 
     /* Restrict values according to masks */
-    of_match_values_mask(match);
+    of_memmask(&match->fields, &match->masks, sizeof(match->fields));
     return value;
 }