diff --git a/src/main.c b/src/main.c
index dce2f9fd..d78ee133 100644
--- a/src/main.c
+++ b/src/main.c
@@ -57,7 +57,7 @@
 #include "ply-progress.h"
 
 #ifndef PLY_MAX_COMMAND_LINE_SIZE
-#define PLY_MAX_COMMAND_LINE_SIZE 512
+#define PLY_MAX_COMMAND_LINE_SIZE 4097
 #endif
 
 #define BOOT_DURATION_FILE     PLYMOUTH_TIME_DIRECTORY "/boot-duration"
@@ -1703,7 +1703,7 @@ get_kernel_command_line (state_t *state)
         }
 
         ply_trace ("reading kernel command line");
-        if (read (fd, state->kernel_command_line, sizeof(state->kernel_command_line)) < 0) {
+        if (read (fd, state->kernel_command_line, sizeof(state->kernel_command_line) - 1) < 0) {
                 ply_trace ("couldn't read it: %m");
                 close (fd);
                 return false;