diff --git a/runtest.rb b/runtest.rb
index 2bb70ee..ce3b551 100755
--- a/runtest.rb
+++ b/runtest.rb
@@ -137,7 +137,7 @@
   # GNU make 4.0 has this output.
   expected.gsub!(/Makefile:\d+: commands for target ".*?" failed\n/, '')
   # We treat some warnings as errors.
-  expected.gsub!(/^\/bin\/sh: line 0: /, '')
+  expected.gsub!(/^\/bin\/(ba)?sh: line 0: /, '')
   # We print out some ninja warnings in some tests to match what we expect
   # ninja to produce. Remove them if we're not testing ninja.
   if !via_ninja
@@ -168,6 +168,8 @@
   output
 end
 
+bash_var = ' SHELL=/bin/bash'
+
 run_make_test = proc do |mk|
   c = File.read(mk)
   expected_failure = false
@@ -219,6 +221,7 @@
       if via_ninja || is_silent_test
         cmd += ' -s'
       end
+      cmd += bash_var
       cmd += " #{tc} 2>&1"
       res = `#{cmd}`
       res = normalize_make_log(res, mk, via_ninja)
@@ -246,6 +249,7 @@
       if is_silent_test
         cmd += ' -s'
       end
+      cmd += bash_var
       if !gen_all_targets || mk =~ /makecmdgoals/
         cmd += " #{tc}"
       end
@@ -328,6 +332,7 @@
     if is_ninja_test
       cmd += ' -s'
     end
+    cmd += bash_var
     expected = IO.popen(cmd, 'r:binary', &:read)
     cleanup
 
@@ -344,6 +349,7 @@
         cmd = "sh ../../#{sh} ../../kati --use_cache -log_dir=."
       end
     end
+    cmd += bash_var
 
     output = IO.popen(cmd, 'r:binary', &:read)
 
diff --git a/testcase/shell_var.mk b/testcase/shell_var.mk
index 8f5de31..b42b0c9 100644
--- a/testcase/shell_var.mk
+++ b/testcase/shell_var.mk
@@ -1,11 +1,11 @@
 $(info $(SHELL))
 
-SHELL:=/bin/echo
+override SHELL:=/bin/echo
 
 $(info $(shell foo))
 
 echo=/bin/echo
-SHELL=$(echo)
+override SHELL=$(echo)
 
 $(info $(shell bar))
 
diff --git a/testcase/shell_var_with_args.mk b/testcase/shell_var_with_args.mk
index ca7b54a..779fa12 100644
--- a/testcase/shell_var_with_args.mk
+++ b/testcase/shell_var_with_args.mk
@@ -2,7 +2,7 @@
 
 export FOO=-x
 
-SHELL := PS4="cmd: " /bin/bash $${FOO}
+override SHELL := PS4="cmd: " /bin/bash $${FOO}
 $(info $(shell echo foo))
 
 test: