diff --git a/src/kernel/move.c b/src/kernel/move.c
index 9912ad4a6..c2a17f9c6 100644
--- a/src/kernel/move.c
+++ b/src/kernel/move.c
@@ -891,17 +891,17 @@ static unit *bewegung_blockiert_von(unit * reisender, region * r)
     }
     if (guard) {
         prob += base_prob;          /* 30% base chance */
-        prob = +guard_count*guard_number_prob;
-        if (r->terrain = newterrain(T_GLACIER))
-            prob = +region_type_prob*2;
-        if (r->terrain = newterrain(T_SWAMP))
-            prob = +region_type_prob*2;
-        if (r->terrain = newterrain(T_MOUNTAIN))
-            prob = +region_type_prob;
-        if (r->terrain = newterrain(T_VOLCANO))
-            prob = +region_type_prob;
-        if (r->terrain = newterrain(T_VOLCANO_SMOKING))
-            prob = +region_type_prob;
+        prob += guard_count*guard_number_prob;
+        if (r->terrain == newterrain(T_GLACIER))
+            prob += region_type_prob * 2;
+        if (r->terrain == newterrain(T_SWAMP))
+            prob += region_type_prob * 2;
+        if (r->terrain == newterrain(T_MOUNTAIN))
+            prob += region_type_prob;
+        if (r->terrain == newterrain(T_VOLCANO))
+            prob += region_type_prob;
+        if (r->terrain == newterrain(T_VOLCANO_SMOKING))
+            prob += region_type_prob;
 
         if (prob > 0 && chance(prob)) {
             return guard;