diff --git a/Doxyfile b/Doxyfile
index b77de55d..344c077f 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -767,7 +767,7 @@ INPUT                  = . \
                          GNUmakefile \
                          GNUmakefile-cross \
                          rdrand.asm \
-                         rdrand.S
+                         rdrand.s
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
diff --git a/Filelist.txt b/Filelist.txt
index 0d4d1bcf..b4f9735a 100644
--- a/Filelist.txt
+++ b/Filelist.txt
@@ -210,7 +210,7 @@ rc6.cpp
 rc6.h
 rdrand-masm.cmd
 rdrand-nasm.sh
-rdrand.S
+rdrand.s
 rdrand.asm
 rdrand.cpp
 rdrand.h
diff --git a/GNUmakefile b/GNUmakefile
index a666c357..d26434d6 100755
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -704,21 +704,21 @@ endif
 .PHONY: trim
 trim:
 ifneq ($(IS_DARWIN),0)
-	sed -i '' -e's/[[:space:]]*$$//' *.sh *.h *.cpp *.asm *.S *.sln *.vcxproj *.filters GNUmakefile GNUmakefile-cross
+	sed -i '' -e's/[[:space:]]*$$//' *.sh *.h *.cpp *.asm *.s *.sln *.vcxproj *.filters GNUmakefile GNUmakefile-cross
 	make convert
 else
-	sed -i -e's/[[:space:]]*$$//' *.sh *.h *.cpp *.asm *.S *.sln *.vcxproj *.filters GNUmakefile GNUmakefile-cross
+	sed -i -e's/[[:space:]]*$$//' *.sh *.h *.cpp *.asm *.s *.sln *.vcxproj *.filters GNUmakefile GNUmakefile-cross
 	make convert
 endif
 
 .PHONY: convert
 convert:
 	@-$(CHMOD) 0700 TestVectors/ TestData/ TestScripts/
-	@-$(CHMOD) 0600 $(TEXT_FILES) *.asm *.S *.zip *.cmake TestVectors/*.txt TestData/*.dat
+	@-$(CHMOD) 0600 $(TEXT_FILES) *.asm *.s *.zip *.cmake TestVectors/*.txt TestData/*.dat
 	@-$(CHMOD) 0700 $(EXEC_FILES) *.sh *.cmd TestScripts/*.sh TestScripts/*.pl TestScripts/*.cmd
 	@-$(CHMOD) 0700 *.cmd *.sh GNUmakefile GNUmakefile-cross TestScripts/*.sh TestScripts/*.pl
 	-unix2dos --keepdate --quiet $(TEXT_FILES) *.asm *.cmd *.cmake TestScripts/*.pl TestScripts/*.cmd
-	-dos2unix --keepdate --quiet GNUmakefile GNUmakefile-cross *.S *.sh TestScripts/*.sh
+	-dos2unix --keepdate --quiet GNUmakefile GNUmakefile-cross *.s *.sh TestScripts/*.sh
 ifneq ($(IS_DARWIN),0)
 	@-xattr -c *
 endif
@@ -764,7 +764,7 @@ endif # Dependencies
 
 # Run rdrand-nasm.sh to create the object files
 ifeq ($(USE_NASM),1)
-rdrand.o: rdrand.h rdrand.cpp rdrand.S
+rdrand.o: rdrand.h rdrand.cpp rdrand.s
 	$(CXX) $(strip $(CXXFLAGS)) -DNASM_RDRAND_ASM_AVAILABLE=1 -DNASM_RDSEED_ASM_AVAILABLE=1 -c rdrand.cpp
 rdrand-%.o:
 	./rdrand-nasm.sh
diff --git a/rdrand-nasm.sh b/rdrand-nasm.sh
index 8fb68597..0cdf1c04 100755
--- a/rdrand-nasm.sh
+++ b/rdrand-nasm.sh
@@ -20,39 +20,39 @@ fi
 
 if [ "$IS_LINUX" -eq "1" ]; then
     echo "Building rdrand and rdseed modules for Linux"
-    nasm -f elf32 rdrand.S -DX86 -g -o rdrand-x86.o
-    nasm -f elfx32 rdrand.S -DX32 -g -o rdrand-x32.o
-    nasm -f elf64 rdrand.S -DX64 -g -o rdrand-x64.o
+    nasm -f elf32 rdrand.s -DX86 -g -o rdrand-x86.o
+    nasm -f elfx32 rdrand.s -DX32 -g -o rdrand-x32.o
+    nasm -f elf64 rdrand.s -DX64 -g -o rdrand-x64.o
     SUCCESS=1
 fi
 
 if [ "$IS_OPENBSD" -eq "1" ] || [ "$IS_NETBSD" -eq "1" ] || [ "$IS_FREEBSD" -eq "1" ] || [ "$IS_DRAGONFLY" -eq "1" ]; then
     echo "Building rdrand and rdseed modules for BSD"
-    nasm -f elf32 rdrand.S -DX86 -g -o rdrand-x86.o
-    nasm -f elfx32 rdrand.S -DX32 -g -o rdrand-x32.o
-    nasm -f elf64 rdrand.S -DX64 -g -o rdrand-x64.o
+    nasm -f elf32 rdrand.s -DX86 -g -o rdrand-x86.o
+    nasm -f elfx32 rdrand.s -DX32 -g -o rdrand-x32.o
+    nasm -f elf64 rdrand.s -DX64 -g -o rdrand-x64.o
     SUCCESS=1
 fi
 
 if [ "$IS_SOLARIS" -eq "1" ]; then
     echo "Building rdrand and rdseed modules for Solaris"
-    nasm -f elf32 rdrand.S -DX86 -o rdrand-x86.o
-    nasm -f elfx32 rdrand.S -DX32 -o rdrand-x32.o
-    nasm -f elf64 rdrand.S -DX64 -o rdrand-x64.o
+    nasm -f elf32 rdrand.s -DX86 -o rdrand-x86.o
+    nasm -f elfx32 rdrand.s -DX32 -o rdrand-x32.o
+    nasm -f elf64 rdrand.s -DX64 -o rdrand-x64.o
     SUCCESS=1
 fi
 
 if [ "$IS_DARWIN" -eq "1" ]; then
     echo "Building rdrand and rdseed modules for Darwin"
-    nasm -f macho32 rdrand.S -DDARWIN -DX86 -g -o rdrand-x86.o
-    nasm -f macho64 rdrand.S -DDARWIN -DX64 -g -o rdrand-x64.o
+    nasm -f macho32 rdrand.s -DDARWIN -DX86 -g -o rdrand-x86.o
+    nasm -f macho64 rdrand.s -DDARWIN -DX64 -g -o rdrand-x64.o
     SUCCESS=1
 fi
 
 if [ "$IS_CYGWIN" -eq "1" ]; then
     echo "Building rdrand and rdseed modules for Cygwin"
-    nasm -f win32 rdrand.S -DCYGWIN -DX86 -g -o rdrand-x86.o
-    nasm -f win64 rdrand.S -DCYGWIN -DX64 -g -o rdrand-x64.o
+    nasm -f win32 rdrand.s -DCYGWIN -DX86 -g -o rdrand-x86.o
+    nasm -f win64 rdrand.s -DCYGWIN -DX64 -g -o rdrand-x64.o
     SUCCESS=1
 fi
 
diff --git a/rdrand.s b/rdrand.s
index 474a6832..d46d2c8e 100644
--- a/rdrand.s
+++ b/rdrand.s
@@ -6,9 +6,9 @@
 ;; of intrinsics. The routines below run a little faster than the intrinsic
 ;; based routines.
 
-;; nasm -f elf32 rdrand.S -DX86 -g -o rdrand-x86.o
-;; nasm -f elfx32 rdrand.S -DX32 -g -o rdrand-x32.o
-;; nasm -f elf64 rdrand.S -DX64 -g -o rdrand-x64.o
+;; nasm -f elf32 rdrand.s -DX86 -g -o rdrand-x86.o
+;; nasm -f elfx32 rdrand.s -DX32 -g -o rdrand-x32.o
+;; nasm -f elf64 rdrand.s -DX64 -g -o rdrand-x64.o
 
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