diff --git a/icu4c/source/acinclude.m4 b/icu4c/source/acinclude.m4
index aeadc2c664a..797a2963770 100644
--- a/icu4c/source/acinclude.m4
+++ b/icu4c/source/acinclude.m4
@@ -262,7 +262,7 @@ AC_DEFUN([AC_CHECK_64BIT_LIBS],
                     if test "$CAN_BUILD_64" != yes; then
                         # Nope. back out changes.
                         CFLAGS="${CFLAGS_OLD}"
-                        CXXFLAGS="${CFLAGS_OLD}"
+                        CXXFLAGS="${CXXFLAGS_OLD}"
                         # 2. try xarch=v9 [deprecated]
                         ## TODO: cross compile: the following won't work.
                         SPARCV9=`isainfo -n 2>&1 | grep sparcv9`
@@ -457,9 +457,6 @@ AC_DEFUN([AC_CHECK_STRICT_COMPILE],
         if test "$GCC" = yes
         then
             case "${host}" in
-            *-*-solaris*)
-                # Don't use -std=c99 option on Solaris/GCC
-                ;;
             *)
                 # Do not use -ansi. It limits us to C90, and it breaks some platforms.
                 # We use -std=c99 to disable the gnu99 defaults and its associated warnings
diff --git a/icu4c/source/config/mh-solaris-gcc b/icu4c/source/config/mh-solaris-gcc
index 313e1ab6373..eac6d2fb005 100644
--- a/icu4c/source/config/mh-solaris-gcc
+++ b/icu4c/source/config/mh-solaris-gcc
@@ -9,8 +9,8 @@ SHAREDLIBCXXFLAGS = -fPIC
 SHAREDLIBCPPFLAGS = -DPIC
 
 ## Commands to generate dependency files
-GEN_DEPS.c= 	$(CC) -E -MM $(DEFS) $(CPPFLAGS)
-GEN_DEPS.cc=	$(CXX) -E -MM $(DEFS) $(CPPFLAGS)
+GEN_DEPS.c= 	$(CC) -E -MM $(DEFS) $(CPPFLAGS) $(CFLAGS)
+GEN_DEPS.cc=	$(CXX) -E -MM $(DEFS) $(CPPFLAGS) $(CXXFLAGS)
 
 ## These are the library specific LDFLAGS
 LDFLAGSICUDT=-nodefaultlibs -nostdlib