diff --git a/src/gnuwin32/MkRules.rules b/src/gnuwin32/MkRules.rules
index f7c2752c489..362e91d37a3 100644
--- a/src/gnuwin32/MkRules.rules
+++ b/src/gnuwin32/MkRules.rules
@@ -156,7 +156,9 @@ ifndef USE_LLVM
   FLIBS=-lgfortran -lquadmath
 else
   FC=$(BINPREF)flang $(M_ARCH)
-  FLIBS=-lFortranRuntime -lFortranDecimal -lFortran_main -lc++
+  ## Fortran_main is needed/available only in some builds of llvm/flang-new
+  LIBFM = $(or $(and $(wildcard $(EXT_LIBS)/lib/libFortran_main.a),-lFortran_main),)
+  FLIBS=-lFortranRuntime -lFortranDecimal $(LIBFM) -lc++ -lm
 endif
 LINKER=$(MAIN_LD)
 MAIN_LD=$(CC)
diff --git a/src/gnuwin32/fixed/Makefile b/src/gnuwin32/fixed/Makefile
index 290ae4194e5..131f100d1d5 100644
--- a/src/gnuwin32/fixed/Makefile
+++ b/src/gnuwin32/fixed/Makefile
@@ -46,6 +46,7 @@ fixetc: $(ETC) ../MkRules Makefile
 	  -e "s@NM_FILTER =@NM_FILTER = $(NM_FILTER)@" \
 	  -e "s|LTO =|LTO = $(LTO)|" \
 	  -e "s|LTO_OPT =|LTO_OPT = $(LTO_OPT)|" \
+	  -e "s|FLIBS =|FLIBS = $(FLIBS)|" \
 	  etc/Makeconf > $(R_HOME)/etc$(R_ARCH)/Makeconf
 	$(SED) -e "s+@BINDIR@+$(BINDIR)+" \
 	   -e "s+@USE_LLVM@+$(USE_LLVM)+" \
diff --git a/src/gnuwin32/fixed/etc/Makeconf b/src/gnuwin32/fixed/etc/Makeconf
index 7b04bd48f80..9e117c1e3b5 100644
--- a/src/gnuwin32/fixed/etc/Makeconf
+++ b/src/gnuwin32/fixed/etc/Makeconf
@@ -32,6 +32,7 @@ IMPDIR = bin
 M_ARCH =
 DT_ARCH =
 RC_ARCH =
+FLIBS =
 # Used by packages tcltk and tkrplot
 TCL_HOME = $(R_HOME)/Tcl
 
@@ -154,10 +155,8 @@ F_VISIBILITY =
 ## FC is the compiler used for all Fortran as from R 3.6.0
 ifdef USE_LLVM
   FC = $(BINPREF)flang $(M_ARCH)
-  FLIBS = -lFortranRuntime -lFortranDecimal -lFortran_main -lc++ -lm 
 else
   FC = $(BINPREF)gfortran $(M_ARCH)
-  FLIBS = -lgfortran -lm -lquadmath
 endif
 FCFLAGS = -O3 $(FDEBUGFLAG) @EOPTS@ $(LTO)
 ## additional libs needed when linking with $(FC), e.g. on some Oracle compilers