diff --git a/src/libopensc/ctx.c b/src/libopensc/ctx.c
index 46dcce49..626686a7 100644
--- a/src/libopensc/ctx.c
+++ b/src/libopensc/ctx.c
@@ -178,11 +178,13 @@ sc_ctx_win32_get_config_value(const char *name_env,
 
 	if (name_env)   {
 		char *value = value = getenv(name_env);
-		if (strlen(value) < *out_len)
-			return SC_ERROR_NOT_ENOUGH_MEMORY;
-		memcpy(out, value, strlen(value));
-		*out_len = strlen(value);
-		return SC_SUCCESS;
+		if (value) {
+			if (strlen(value) < *out_len)
+				return SC_ERROR_NOT_ENOUGH_MEMORY;
+			memcpy(out, value, strlen(value));
+			*out_len = strlen(value);
+			return SC_SUCCESS;
+		}
 	}
 
 	if (!name_reg)