diff --git a/filter/data.c b/filter/data.c
index 276738a9..2bb5920c 100644
--- a/filter/data.c
+++ b/filter/data.c
@@ -192,7 +192,7 @@ val_compare(const struct f_val *v1, const struct f_val *v2)
     if (val_is_ip4(v1) && (v2->type == T_QUAD))
       return uint_cmp(ipa_to_u32(v1->val.ip), v2->val.i);
 
-    debug( "Types do not match in val_compare\n" );
+    DBG( "Types do not match in val_compare\n" );
     return F_CMP_ERROR;
   }
 
diff --git a/filter/decl.m4 b/filter/decl.m4
index fc26e193..a2a8c88a 100644
--- a/filter/decl.m4
+++ b/filter/decl.m4
@@ -186,6 +186,12 @@ if (f$1->type && f$2->type && (f$1->type != f$2->type) &&
   cf_error("Arguments $1 and $2 of %s must be of the same type", f_instruction_name(what->fi_code));
 FID_INTERPRET_BODY()')
 
+m4_define(ARG_PREFER_SAME_TYPE, `
+FID_NEW_BODY()m4_dnl
+if (f$1->type && f$2->type && (f$1->type != f$2->type))
+   (void) (f_const_promotion(f$2, f$1->type) || f_const_promotion(f$1, f$2->type));
+FID_INTERPRET_BODY()')
+
 #	Executing another filter line. This replaces the recursion
 #	that was needed in the former implementation.
 m4_define(LINEX, `FID_INTERPRET_EXEC()LINEX_($1)FID_INTERPRET_NEW()return $1 FID_INTERPRET_BODY()')
diff --git a/filter/f-inst.c b/filter/f-inst.c
index d321f06d..500732c6 100644
--- a/filter/f-inst.c
+++ b/filter/f-inst.c
@@ -423,12 +423,14 @@
   INST(FI_NEQ, 2, 1) {
     ARG_ANY(1);
     ARG_ANY(2);
+    ARG_PREFER_SAME_TYPE(1, 2);
     RESULT(T_BOOL, i, !val_same(&v1, &v2));
   }
 
   INST(FI_EQ, 2, 1) {
     ARG_ANY(1);
     ARG_ANY(2);
+    ARG_PREFER_SAME_TYPE(1, 2);
     RESULT(T_BOOL, i, val_same(&v1, &v2));
   }
 
diff --git a/filter/test.conf b/filter/test.conf
index 50c58b3a..401a999b 100644
--- a/filter/test.conf
+++ b/filter/test.conf
@@ -498,8 +498,8 @@ prefix set s1;
 	s0 = [];
 	s1 = [];
 	bt_assert(pxs != s0);
-	bt_assert(pxs  = s1);
-	#bt_assert(pxs  = []);
+	bt_assert(pxs = s1);
+	bt_assert(pxs = []);
 }
 
 function t_prefix_set()
@@ -507,7 +507,7 @@ prefix set pxs;
 {
 	pxs = [];
 	bt_assert(format(pxs) = "[]");
-	#bt_assert(pxs = []);
+	bt_assert(pxs = []);
 	bt_assert(1.2.0.0/16 !~ []);
 	bt_assert(1.2.0.0/16 !~ pxs);
 
@@ -600,7 +600,7 @@ prefix set pxs;
 {
 	pxs = [];
 	bt_assert(format(pxs) = "[]");
-	#bt_assert(pxs = []);
+	bt_assert(pxs = []);
 	bt_assert(12::34/128 !~ []);
 	bt_assert(12::34/128 !~ pxs);