diff --git a/src/kernel/config.h b/src/kernel/config.h
index c8fc106e6..ade8bfa63 100644
--- a/src/kernel/config.h
+++ b/src/kernel/config.h
@@ -261,7 +261,7 @@ extern "C" {
         unsigned int data_turn;
         struct param *parameters;
         void *vm_state;
-        float producexpchance;
+        double producexpchance;
         int cookie;
         int data_version; /* TODO: eliminate in favor of gamedata.version */
         struct _dictionary_ *inifile;
diff --git a/src/kernel/unit.c b/src/kernel/unit.c
index 5fb841d9a..696015aef 100644
--- a/src/kernel/unit.c
+++ b/src/kernel/unit.c
@@ -1935,7 +1935,12 @@ bool unit_can_study(const unit *u) {
 }
 
 static double produceexp_chance(void) {
-    return get_param_flt(global.parameters, "study.from_use", 1.0 / 3);
+    static int update = 0;
+    if (update != global.cookie) {
+        global.producexpchance = get_param_flt(global.parameters, "study.from_use", 1.0 / 3);
+        update = global.cookie;
+    }
+    return global.producexpchance;
 }
 
 void produceexp_ex(struct unit *u, skill_t sk, int n, bool (*learn)(unit *, skill_t, double))