diff --git a/src/common/kernel/save.c b/src/common/kernel/save.c
index b9c38430e..ca4052d25 100644
--- a/src/common/kernel/save.c
+++ b/src/common/kernel/save.c
@@ -2051,6 +2051,7 @@ writegame(char *path, char quiet)
 #else
 			for (i=0;i!=u->skill_size;++i) {
 				skill * sv = u->skills+i;
+				assert(sv->level>=0 && sv->learning>=0 && sv->learning<=sv->level*2);
 				if (sv->learning || sv->level) {
 					wi(F, sv->id);
 					wi(F, sv->level);
diff --git a/src/common/kernel/skill.c b/src/common/kernel/skill.c
index 035ab9c9d..c91536307 100644
--- a/src/common/kernel/skill.c
+++ b/src/common/kernel/skill.c
@@ -259,26 +259,28 @@ level(int days)
 void 
 reduce_skill(skill * sv, int change)
 {
-	int weeks = (sv->level * sv->level - sv->level) / 2 + sv->learning;
 	if (sv->learning>=change) {
 		/* just forget a few weeks */
-		weeks -= change;
+		sv->learning = (unsigned char)(sv->learning-change);
 	} else {
+		int weeks;
 		change -= sv->learning;
 		while (change>=sv->level && sv->level > 0) {
 			change -= sv->level;
 			--sv->level;
 		}
-		if (change && change<sv->level) {
+		if (change && sv->level > 0 && change<sv->level) {
 			/* this is not an exact science... it would be better to set
 			 * sv->learning so that the average time to rise was = change.
 			 */
+			--sv->level;
 			weeks = (sv->level-change)*2;
 		} else {
 			weeks = 0;
 		}
+		sv->learning = (unsigned char)weeks;
 	}
-	sv->learning = (unsigned char)weeks;
+	assert(sv->level>=0 && sv->learning>=0 && sv->learning<=sv->level*2);
 }
 
 int 
diff --git a/src/res/de/messages.xml b/src/res/de/messages.xml
index e0ab39327..04710e4ae 100644
--- a/src/res/de/messages.xml
+++ b/src/res/de/messages.xml
@@ -4559,8 +4559,8 @@
 			<arg name="target" type="unit"></arg>
 			<arg name="report" type="string"></arg>
 		</type>
-		<text locale="de">"$unit($spy) gelang es Informationen über $unit(target) herauszubekommen: '$report'."</text>
-		<text locale="en">"$unit($spy) managed to gather Information about $unit(target): '$report'."</text>
+		<text locale="de">"$unit($spy) gelang es Informationen über $unit($target) herauszubekommen: '$report'."</text>
+		<text locale="en">"$unit($spy) managed to gather information about $unit($target): '$report'."</text>
 	</message>
 
 	<message name="spyfail" section="events">