diff --git a/src/maprules.c b/src/maprules.c
index 6060a03..c852082 100644
--- a/src/maprules.c
+++ b/src/maprules.c
@@ -76,10 +76,12 @@
 #define PR_DEBUG(s)		fprintf(stderr,s)
 #define PR_DEBUG1(s,a)		fprintf(stderr,s,a)
 #define PR_DEBUG2(s,a,b)	fprintf(stderr,s,a,b)
+#define PR_DEBUG3(s,a,b,c)	fprintf(stderr,s,a,b,c)
 #else
 #define PR_DEBUG(s)
 #define PR_DEBUG1(s,a)
 #define PR_DEBUG2(s,a,b)
+#define PR_DEBUG3(s,a,b,c)
 #endif
 
 /***====================================================================***/
@@ -608,14 +610,17 @@ FreeMultiDefs(XkbRF_MultiDefsPtr defs)
 }
 
 static void
-Apply(char *src, char **dst)
+Apply(char *desc, char *src, char **dst)
 {
     if (src) {
         if (*src == '+' || *src == '!') {
+            PR_DEBUG3("Adding %s: was [%s], appending  [%s]\n", desc, *dst, src);
 	    *dst= _Concat(*dst, src);
         } else {
-            if (*dst == NULL)
+            if (*dst == NULL) {
 	        *dst= _XkbDupString(src);
+                PR_DEBUG2("Setting %s to [%s]\n", desc, src);
+            }
         }
     }
 }
@@ -624,14 +629,18 @@ static void
 XkbRF_ApplyRule(	XkbRF_RulePtr 		rule,
 			XkbComponentNamesPtr	names)
 {
-    rule->flags&= ~XkbRF_PendingMatch; /* clear the flag because it's applied */
-
-    Apply(rule->keycodes, &names->keycodes);
-    Apply(rule->symbols,  &names->symbols);
-    Apply(rule->types,    &names->types);
-    Apply(rule->compat,   &names->compat);
-    Apply(rule->geometry, &names->geometry);
-    Apply(rule->keymap,   &names->keymap);
+    if (rule->flags & XkbRF_PendingMatch) {
+        PR_DEBUG("Applying the deferred rule: ");
+        rule->flags&= ~XkbRF_PendingMatch; /* clear the flag because it's applied */
+    } else
+        PR_DEBUG("Applying the immediate rule: ");
+
+    Apply("keycodes", rule->keycodes, &names->keycodes);
+    Apply("symbols", rule->symbols,  &names->symbols);
+    Apply("types", rule->types,    &names->types);
+    Apply("compat", rule->compat,   &names->compat);
+    Apply("geometry", rule->geometry, &names->geometry);
+    Apply("keymap", rule->keymap,   &names->keymap);
 }
 
 static Bool
@@ -666,67 +675,117 @@ XkbRF_CheckApplyRule(	XkbRF_RulePtr 		rule,
 {
     Bool pending = False;
 
+    PR_DEBUG1("The rule from group %d.", rule->number);
+
     if (rule->model != NULL) {
+        PR_DEBUG2("  Model: \"%s\" in the rule, requested \"%s\": ",
+                  rule->model,
+                  mdefs->model);
         if(mdefs->model == NULL)
             return 0;
         if (strcmp(rule->model, "*") == 0) {
+            PR_DEBUG("wildcard.");
             pending = True;
         } else {
             if (rule->model[0] == '$') {
-               if (!CheckGroup(rules, rule->model, mdefs->model))
+               PR_DEBUG1("checking against the list \"%s\": ", rule->model);
+               if (!CheckGroup(rules, rule->model, mdefs->model)) {
+                  PR_DEBUG("ignore.\n");
                   return 0;
+               }
+               PR_DEBUG("match.");
             } else {
-	       if (strcmp(rule->model, mdefs->model) != 0)
+	       if (strcmp(rule->model, mdefs->model) != 0) {
+                  PR_DEBUG("ignore.\n");
 	          return 0;
+               }
+               PR_DEBUG("match.");
 	    }
 	}
     }
     if (rule->option != NULL) {
-	if (mdefs->options == NULL)
+        PR_DEBUG2("  Option(s): \"%s\" in the rule, requested \"%s\": ",
+                  rule->option,
+                  mdefs->options);
+	if (mdefs->options == NULL) {
+            PR_DEBUG("no input.\n");
 	    return 0;
-	if ((!MatchOneOf(rule->option,mdefs->options)))
+        }
+	if ((!MatchOneOf(rule->option,mdefs->options))) {
+            PR_DEBUG("ignore.\n");
 	    return 0;
+        }
     }
 
     if (rule->layout != NULL) {
+        PR_DEBUG3("  Layout[%d]: \"%s\" in the rule, requested \"%s\": ",
+                  rule->layout_num,
+                  rule->layout,
+                  mdefs->layout[rule->layout_num]);
 	if(mdefs->layout[rule->layout_num] == NULL ||
-	   *mdefs->layout[rule->layout_num] == '\0')
+	   *mdefs->layout[rule->layout_num] == '\0') {
+            PR_DEBUG("no input.\n");
 	    return 0;
+        }
         if (strcmp(rule->layout, "*") == 0) {
+            PR_DEBUG("wildcard.");
             pending = True;
         } else {
             if (rule->layout[0] == '$') {
+               PR_DEBUG1("checking against the list \"%s\": ", rule->layout);
                if (!CheckGroup(rules, rule->layout,
-                               mdefs->layout[rule->layout_num]))
+                               mdefs->layout[rule->layout_num])) {
+                  PR_DEBUG("ignore.\n");
                   return 0;
+               }
+               PR_DEBUG("match.");
 	    } else {
-	       if (strcmp(rule->layout, mdefs->layout[rule->layout_num]) != 0)
-	           return 0;
+	       if (strcmp(rule->layout, mdefs->layout[rule->layout_num]) != 0) {
+                  PR_DEBUG("ignore.\n");
+	          return 0; 
+               }
+               PR_DEBUG("match.");
 	    }
 	}
     }
     if (rule->variant != NULL) {
+        PR_DEBUG3("  Variant[%d]: \"%s\" in the rule, requested \"%s\": ",
+                  rule->variant_num,
+                  rule->variant,
+                  mdefs->variant[rule->variant_num]);
 	if (mdefs->variant[rule->variant_num] == NULL ||
-	    *mdefs->variant[rule->variant_num] == '\0')
+	    *mdefs->variant[rule->variant_num] == '\0') {
+            PR_DEBUG("no input.\n");
 	    return 0;
+        }
         if (strcmp(rule->variant, "*") == 0) {
+            PR_DEBUG("wildcard.");
             pending = True;
         } else {
             if (rule->variant[0] == '$') {
+               PR_DEBUG1("checking against the list \"%s\": ", rule->variant);
                if (!CheckGroup(rules, rule->variant,
-                               mdefs->variant[rule->variant_num]))
+                               mdefs->variant[rule->variant_num])) {
+                  PR_DEBUG("ignore.\n");
                   return 0;
+               }
+               PR_DEBUG("match.");
             } else {
 	       if (strcmp(rule->variant,
-                          mdefs->variant[rule->variant_num]) != 0)
+                          mdefs->variant[rule->variant_num]) != 0) {
+                   PR_DEBUG("ignore.\n");
 	           return 0;
+               }
+               PR_DEBUG("match.");
 	    }
 	}
     }
     if (pending) {
         rule->flags|= XkbRF_PendingMatch;
+        PR_DEBUG("  The rule is to apply later.\n");
 	return rule->number;
     }
+    PR_DEBUG("  The rule is to apply immediately.\n");
     /* exact match, apply it now */
     XkbRF_ApplyRule(rule,names);
     return rule->number;