diff --git a/unicode/norm/composition.go b/unicode/norm/composition.go
index 9f37ef0..e2087bc 100644
--- a/unicode/norm/composition.go
+++ b/unicode/norm/composition.go
@@ -461,6 +461,10 @@
 // It should only be used to recompose a single segment, as it will not
 // handle alternations between Hangul and non-Hangul characters correctly.
 func (rb *reorderBuffer) compose() {
+	// Lazily load the map used by the combine func below, but do
+	// it outside of the loop.
+	recompMapOnce.Do(buildRecompMap)
+
 	// UAX #15, section X5 , including Corrigendum #5
 	// "In any character sequence beginning with starter S, a character C is
 	//  blocked from S if and only if there is some character B between S
diff --git a/unicode/norm/forminfo.go b/unicode/norm/forminfo.go
index f7fbf86..526c703 100644
--- a/unicode/norm/forminfo.go
+++ b/unicode/norm/forminfo.go
@@ -199,9 +199,14 @@
 // Note that the recomposition map for NFC and NFKC are identical.
 
 // combine returns the combined rune or 0 if it doesn't exist.
+//
+// The caller is responsible for calling
+// recompMapOnce.Do(buildRecompMap) sometime before this is called.
 func combine(a, b rune) rune {
 	key := uint32(uint16(a))<<16 + uint32(uint16(b))
-	recompMapOnce.Do(buildRecompMap)
+	if recompMap == nil {
+		panic("caller error") // see func comment
+	}
 	return recompMap[key]
 }