diff --git a/icu4c/source/i18n/choicfmt.cpp b/icu4c/source/i18n/choicfmt.cpp
index 59ded53ceda..ffc06bacc3b 100644
--- a/icu4c/source/i18n/choicfmt.cpp
+++ b/icu4c/source/i18n/choicfmt.cpp
@@ -243,7 +243,7 @@ ChoiceFormat::stod(const UnicodeString& string)
     char source[256];
     char* end;
 
-    string.extract(0, string.length(), source, 256, "");    /* invariant codepage */
+    source[string.extract(0, string.length(), source, 256, "")] = 0;    /* invariant codepage */
     return uprv_strtod(source,&end);
 }