diff --git a/build_rte_rrtmgp.sh b/build_rte_rrtmgp.sh
index c253ce4..05a0972 100755
--- a/build_rte_rrtmgp.sh
+++ b/build_rte_rrtmgp.sh
@@ -1,7 +1,9 @@
-# /bin/bash
+#!/bin/sh
 
-if [ -n "$CONDA_PREFIX" ] && [ "$OS" == *"Windows"* ] || [ -z "$CONDA_PREFIX" ]; then
+if [ -n "$CONDA_PREFIX" ] && [ "$OS" = *"Windows"* ]; then
+    export FC=gfortran
+elif [ -z "$CONDA_PREFIX" ]; then
     export FC=gfortran
 fi
 
-make -C rte-rrtmgp/build -j 2
\ No newline at end of file
+make -C rte-rrtmgp/build -j 2