diff --git a/core/bootstrap/primitives.factor b/core/bootstrap/primitives.factor
index 233de6f4ee..9d3c28b068 100755
--- a/core/bootstrap/primitives.factor
+++ b/core/bootstrap/primitives.factor
@@ -732,6 +732,8 @@ define-builtin
     { "set-innermost-frame-quot" "kernel.private" }
     { "call-clear" "kernel" }
     { "(os-envs)" "system.private" }
+    { "set-os-env" "system" }
+    { "unset-os-env" "system" }
     { "(set-os-envs)" "system.private" }
     { "resize-byte-array" "byte-arrays" }
     { "resize-bit-array" "bit-arrays" }
diff --git a/core/inference/known-words/known-words.factor b/core/inference/known-words/known-words.factor
index 33a5da87f4..453e2460b0 100755
--- a/core/inference/known-words/known-words.factor
+++ b/core/inference/known-words/known-words.factor
@@ -587,6 +587,10 @@ set-primitive-effect
 
 \ (os-envs) { } { array } <effect> set-primitive-effect
 
+\ set-os-env { string string } { } <effect> set-primitive-effect
+
+\ unset-os-env { string } { } <effect> set-primitive-effect
+
 \ (set-os-envs) { array } { } <effect> set-primitive-effect
 
 \ do-primitive [ \ do-primitive no-effect ] "infer" set-word-prop
diff --git a/vm/os-unix.c b/vm/os-unix.c
index 74320288aa..2991cde78c 100755
--- a/vm/os-unix.c
+++ b/vm/os-unix.c
@@ -103,6 +103,21 @@ DEFINE_PRIMITIVE(os_envs)
 	dpush(result);
 }
 
+DEFINE_PRIMITIVE(set_os_env)
+{
+	char *key = unbox_char_string();
+	REGISTER_C_STRING(key);
+	char *value = unbox_char_string();
+	UNREGISTER_C_STRING(key);
+	setenv(key, value, 1);
+}
+
+DEFINE_PRIMITIVE(unset_os_env)
+{
+	char *key = unbox_char_string();
+	unsetenv(key);
+}
+
 DEFINE_PRIMITIVE(set_os_envs)
 {
 	F_ARRAY *array = untag_array(dpop());
diff --git a/vm/primitives.c b/vm/primitives.c
index 533fcebc9a..2906a154a2 100755
--- a/vm/primitives.c
+++ b/vm/primitives.c
@@ -182,6 +182,8 @@ void *primitives[] = {
 	primitive_set_innermost_stack_frame_quot,
 	primitive_call_clear,
 	primitive_os_envs,
+	primitive_set_os_env,
+	primitive_unset_os_env,
 	primitive_set_os_envs,
 	primitive_resize_byte_array,
 	primitive_resize_bit_array,
diff --git a/vm/run.h b/vm/run.h
index c112c5f587..e2afb08525 100755
--- a/vm/run.h
+++ b/vm/run.h
@@ -249,6 +249,8 @@ DECLARE_PRIMITIVE(setenv);
 DECLARE_PRIMITIVE(exit);
 DECLARE_PRIMITIVE(os_env);
 DECLARE_PRIMITIVE(os_envs);
+DECLARE_PRIMITIVE(set_os_env);
+DECLARE_PRIMITIVE(unset_os_env);
 DECLARE_PRIMITIVE(set_os_envs);
 DECLARE_PRIMITIVE(eq);
 DECLARE_PRIMITIVE(millis);