diff --git a/icu4c/source/common/localebuilder.cpp b/icu4c/source/common/localebuilder.cpp
index 28ddf514b48..e9caa20b4cc 100644
--- a/icu4c/source/common/localebuilder.cpp
+++ b/icu4c/source/common/localebuilder.cpp
@@ -433,7 +433,7 @@ Locale LocaleBuilder::build(UErrorCode& errorCode)
     return product;
 }
 
-UBool LocaleBuilder::copyErrorTo(UErrorCode &outErrorCode) {
+UBool LocaleBuilder::copyErrorTo(UErrorCode &outErrorCode) const {
     if (U_FAILURE(outErrorCode)) {
         // Do not overwrite the older error code
         return TRUE;
diff --git a/icu4c/source/common/unicode/localebuilder.h b/icu4c/source/common/unicode/localebuilder.h
index 78f7efcfbb8..d3f587caeef 100644
--- a/icu4c/source/common/unicode/localebuilder.h
+++ b/icu4c/source/common/unicode/localebuilder.h
@@ -288,7 +288,7 @@ public:
      * @return TRUE if U_FAILURE(outErrorCode)
      * @draft ICU 65
      */
-    UBool copyErrorTo(UErrorCode &outErrorCode);
+    UBool copyErrorTo(UErrorCode &outErrorCode) const;
 
 private:
     UErrorCode status_;