diff --git a/configure b/configure
index 2b58efe5d..abb5ffef1 100755
--- a/configure
+++ b/configure
@@ -524,7 +524,7 @@ fi
 if [ "$IDN_LIBRARY" = "icu" ]
 then
    IDNA_LIBS="$ICU_FLAGS"
-   CFLAGS="$CFLAGS -DUSE_STRINGPREP_ICU"
+   IDNA_FLAGS="-DUSE_STRINGPREP_ICU"
 fi
 if [ "$IDN_LIBRARY" = "idn" ]
 then
@@ -569,6 +569,7 @@ LUA_INCDIR=$LUA_INCDIR
 LUA_LIBDIR=$LUA_LIBDIR
 LUA_BINDIR=$LUA_BINDIR
 IDN_LIB=$IDN_LIB
+IDNA_FLAGS=$IDNA_FLAGS
 IDNA_LIBS=$IDNA_LIBS
 OPENSSL_LIBS=$OPENSSL_LIBS
 CFLAGS=$CFLAGS
diff --git a/util-src/GNUmakefile b/util-src/GNUmakefile
index 054c92010..e9e063558 100644
--- a/util-src/GNUmakefile
+++ b/util-src/GNUmakefile
@@ -24,6 +24,7 @@ install: $(ALL)
 clean:
 	rm -f $(ALL) $(patsubst %.so,%.o,$(ALL))
 
+encodings.o: CFLAGS+=$(IDNA_FLAGS)
 encodings.so: LDLIBS+=$(IDNA_LIBS)
 
 hashes.so: LDLIBS+=$(OPENSSL_LIBS)
diff --git a/util-src/makefile b/util-src/makefile
index 700633b40..2db415df3 100644
--- a/util-src/makefile
+++ b/util-src/makefile
@@ -23,6 +23,8 @@ install: $(ALL)
 clean:
 	rm -f $(ALL) $(patsubst %.so,%.o,$(ALL))
 
+encodings.o: encodings.c
+	$(CC) $(CFLAGS) $(IDNA_FLAGS) -c -o $@ $<
 encodings.so: encodings.o
 	$(LD) $(LDFLAGS) -o $@ $< $(LDLIBS) $(IDNA_LIBS)