diff --git a/lib/tbb_2020.3/build/windows.inc b/lib/tbb_2020.3/build/windows.inc
index 8c8ca23c1b5..20c6f513242 100644
--- a/lib/tbb_2020.3/build/windows.inc
+++ b/lib/tbb_2020.3/build/windows.inc
@@ -12,7 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+ifeq (true,$(USING_RTOOLS))
+export SHELL = sh.exe
+else
 export SHELL = cmd
+endif
 
 ifdef tbb_build_dir
   test_dir:=$(tbb_build_dir)
@@ -111,7 +115,7 @@ RML.MANIFEST = tbbmanifest.exe.manifest
 endif
 
 MAKE_VERSIONS = $(shell cmd //C "cscript /nologo /E:jscript $(subst \,/,$(tbb_root))/build/version_info_windows.js $(compiler) $(arch) $(subst \,/,\"$(VERSION_FLAGS)\")" > version_string.ver)
-MAKE_TBBVARS  = cmd /C "$(subst /,\,$(tbb_root))\build\generate_tbbvars.bat"
+MAKE_TBBVARS  = cmd //C "$(subst /,\,$(tbb_root))\build\generate_tbbvars.bat"
 
 TEST_LAUNCHER = $(subst /,\,$(tbb_root))\build\test_launcher.bat $(largs)
 
diff --git a/make/libraries b/make/libraries
index be3bba7c849..beba8d1eb24 100644
--- a/make/libraries
+++ b/make/libraries
@@ -143,6 +143,7 @@ ifeq (Windows_NT, $(OS))
   ifeq ($(IS_UCRT),true)
     TBB_CXXFLAGS += -D_UCRT
   endif
+	USING_RTOOLS := true
 endif
 
 # If brackets or spaces are found in MAKE on Windows
@@ -172,11 +173,11 @@ endif
 $(TBB_BIN)/tbb.def: $(TBB_BIN)/tbb-make-check
 	@mkdir -p $(TBB_BIN)
 	touch $(TBB_BIN)/version_$(notdir $(TBB))
-	tbb_root="$(TBB_RELATIVE_PATH)" CXX="$(CXX)" CC="$(TBB_CC)" LDFLAGS='$(LDFLAGS_TBB)' '$(MAKE)' -C "$(TBB_BIN)" -r -f "$(TBB_ABSOLUTE_PATH)/build/Makefile.tbb" compiler=$(TBB_CXX_TYPE) cfg=release stdver=c++1y  CXXFLAGS="$(TBB_CXXFLAGS)"
+	USING_RTOOLS=$(USING_RTOOLS) tbb_root="$(TBB_RELATIVE_PATH)" CXX="$(CXX)" CC="$(TBB_CC)" LDFLAGS='$(LDFLAGS_TBB)' '$(MAKE)' -C "$(TBB_BIN)" -r -f "$(TBB_ABSOLUTE_PATH)/build/Makefile.tbb" compiler=$(TBB_CXX_TYPE) cfg=release stdver=c++1y CXXFLAGS="$(TBB_CXXFLAGS)"
 
 $(TBB_BIN)/tbbmalloc.def: $(TBB_BIN)/tbb-make-check
 	@mkdir -p $(TBB_BIN)
-	tbb_root="$(TBB_RELATIVE_PATH)" CXX="$(CXX)" CC="$(TBB_CC)" LDFLAGS='$(LDFLAGS_TBB)' '$(MAKE)' -C "$(TBB_BIN)" -r -f "$(TBB_ABSOLUTE_PATH)/build/Makefile.tbbmalloc" compiler=$(TBB_CXX_TYPE) cfg=release stdver=c++1y malloc CXXFLAGS="$(TBB_CXXFLAGS)"
+	USING_RTOOLS=$(USING_RTOOLS) tbb_root="$(TBB_RELATIVE_PATH)" CXX="$(CXX)" CC="$(TBB_CC)" LDFLAGS='$(LDFLAGS_TBB)' '$(MAKE)' -C "$(TBB_BIN)" -r -f "$(TBB_ABSOLUTE_PATH)/build/Makefile.tbbmalloc" compiler=$(TBB_CXX_TYPE) cfg=release stdver=c++1y malloc CXXFLAGS="$(TBB_CXXFLAGS)"
 
 $(TBB_BIN)/libtbb.dylib: $(TBB_BIN)/tbb.def
 $(TBB_BIN)/libtbbmalloc.dylib: $(TBB_BIN)/tbbmalloc.def