diff --git a/igvm_c/Makefile b/igvm_c/Makefile
index daea749..73598bc 100644
--- a/igvm_c/Makefile
+++ b/igvm_c/Makefile
@@ -30,7 +30,7 @@ IGVM_LIBS = $(shell pkg-config --libs --static $(UNINSTALLED_PC))
 IGVM_LIBS_STATIC = $(subst $(IGVM_LIBS), -ligvm, $(LIBIGVM))
 
 # Determine igvm crate version from Cargo.toml
-VERSION = $(shell grep -oP "(?<=version = \").+(?=\")" $(IGVM_DIR)/igvm/Cargo.toml)
+VERSION = $(shell sed -n 's/^version = "\(.*\)"/\1/p' $(IGVM_DIR)/igvm/Cargo.toml)
 
 .PHONY: all build test clean install
 
diff --git a/igvm_c/scripts/post_process.sh b/igvm_c/scripts/post_process.sh
index 22cc057..73a5112 100755
--- a/igvm_c/scripts/post_process.sh
+++ b/igvm_c/scripts/post_process.sh
@@ -10,11 +10,13 @@
 # cbindgen configuration files and annotations.
 set -e
 
-sed -i -e 's/INVALID = 0/IGVM_INVALID = 0/g' \
-        -e 's/RESERVED_DO_NOT_USE = /IGVM_RESERVED_DO_NOT_USE = /g' \
-        -e 's/RequiredMemoryFlags/IgvmRequiredMemoryFlags/g' \
-        -e 's/MemoryMapEntryFlags/IgvmMemoryMapEntryFlags/g' \
-        $1/igvm_defs.h
+sed -i.bak -e 's/INVALID = 0/IGVM_INVALID = 0/g' \
+           -e 's/RESERVED_DO_NOT_USE = /IGVM_RESERVED_DO_NOT_USE = /g' \
+           -e 's/RequiredMemoryFlags/IgvmRequiredMemoryFlags/g' \
+           -e 's/MemoryMapEntryFlags/IgvmMemoryMapEntryFlags/g' \
+           "$1/igvm_defs.h"
+rm -f "$1/igvm_defs.h.bak"
 
-sed -i -e 's/  HEADER_SECTION_/  IGVM_HEADER_SECTION_/g' \
-        $1/igvm.h
+sed -i.bak -e 's/  HEADER_SECTION_/  IGVM_HEADER_SECTION_/g' \
+           "$1/igvm.h"
+rm -f "$1/igvm.h.bak"