diff --git a/extras/alloc-pool/Makefile b/extras/alloc-pool/Makefile
index f47b1a5010..6bd6ee575b 100644
--- a/extras/alloc-pool/Makefile
+++ b/extras/alloc-pool/Makefile
@@ -1,8 +1,8 @@
 # For manual testing; say 'make' in extras/alloc-pool and run ./test.
 
-CC=gcc
-DEFS=
-#DEFS+='-DDUK_ALLOC_POOL_DEBUG'
+CC = gcc
+DEFS =
+#DEFS += '-DDUK_ALLOC_POOL_DEBUG'
 
 .PHONY: test
 test:
diff --git a/extras/cbor/Makefile b/extras/cbor/Makefile
index 4820427b34..1e8a6d4121 100644
--- a/extras/cbor/Makefile
+++ b/extras/cbor/Makefile
@@ -1,9 +1,9 @@
 # For manual testing; say 'make' in extras/cbor.
 
-VALGRIND=valgrind
-CC=gcc
-CCOPTS=-std=c99 -Wall -Wextra -O2
-#CCOPTS+=-fsanitize=undefined
+VALGRIND = valgrind
+CC = gcc
+CCOPTS = -std=c99 -Wall -Wextra -O2
+#CCOPTS += -fsanitize=undefined
 
 .PHONY: all
 all: clean jsoncbor test-runs
diff --git a/extras/console/Makefile b/extras/console/Makefile
index a857b20e1e..cfd9ecffd7 100644
--- a/extras/console/Makefile
+++ b/extras/console/Makefile
@@ -1,6 +1,6 @@
 # For manual testing; say 'make' in extras/console and run ./test.
 
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test:
diff --git a/extras/duk-v1-compat/Makefile b/extras/duk-v1-compat/Makefile
index 5ceb606ac3..96bb313036 100644
--- a/extras/duk-v1-compat/Makefile
+++ b/extras/duk-v1-compat/Makefile
@@ -1,6 +1,6 @@
 # For manual testing; say 'make' in extras/duk-v1-compat and run ./test.
 
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test:
diff --git a/extras/logging/Makefile b/extras/logging/Makefile
index 289f13e4b1..0eda5a5620 100644
--- a/extras/logging/Makefile
+++ b/extras/logging/Makefile
@@ -1,6 +1,6 @@
 # For manual testing; say 'make' in extras/logging and run ./test.
 
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test:
diff --git a/extras/minimal-printf/Makefile b/extras/minimal-printf/Makefile
index aaac26ad8b..f969072565 100644
--- a/extras/minimal-printf/Makefile
+++ b/extras/minimal-printf/Makefile
@@ -1,5 +1,5 @@
 # Just for manual testing
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test: duk_minimal_printf.c
diff --git a/extras/module-duktape/Makefile b/extras/module-duktape/Makefile
index 3b727ed039..a0566208a0 100644
--- a/extras/module-duktape/Makefile
+++ b/extras/module-duktape/Makefile
@@ -1,7 +1,7 @@
 # For manual testing; say 'make' in extras/module-duktape and run ./test.
 # There's test coverage in tests/ecmascript, so tests here are very simple.
 
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test:
diff --git a/extras/module-node/Makefile b/extras/module-node/Makefile
index e7a7b994f4..bae55455d4 100644
--- a/extras/module-node/Makefile
+++ b/extras/module-node/Makefile
@@ -1,6 +1,6 @@
 # For manual testing; say 'make' in extras/module-node and run ./test.
 
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test:
diff --git a/extras/print-alert/Makefile b/extras/print-alert/Makefile
index d5156a3b05..e26ec48cbb 100644
--- a/extras/print-alert/Makefile
+++ b/extras/print-alert/Makefile
@@ -1,6 +1,6 @@
 # For manual testing; say 'make' in extras/print-alert and run ./test.
 
-CC	= gcc
+CC = gcc
 
 .PHONY: test
 test: