diff --git a/artiq/firmware/libboard_artiq/slave_fpga.rs b/artiq/firmware/libboard_artiq/slave_fpga.rs
index cd15b87ad..9f97039b3 100644
--- a/artiq/firmware/libboard_artiq/slave_fpga.rs
+++ b/artiq/firmware/libboard_artiq/slave_fpga.rs
@@ -42,11 +42,14 @@ pub fn load() -> Result<(), &'static str> {
         csr::slave_fpga_cfg::oe_write(CCLK_BIT | DIN_BIT | PROGRAM_B_BIT);
 
         csr::slave_fpga_cfg::out_write(0);
-        clock::spin_us(1);  // TPROGRAM=250ns min
+        clock::spin_us(1_000);  // TPROGRAM=250ns min, be_generous
+        if csr::slave_fpga_cfg::in_read() & INIT_B_BIT != 0 {
+            return Err("Slave FPGA did not react to PROGRAM.");
+        }
         csr::slave_fpga_cfg::out_write(PROGRAM_B_BIT);
         clock::spin_us(5_000);  // TPL=5ms max
         if csr::slave_fpga_cfg::in_read() & INIT_B_BIT == 0 {
-            return Err("Slave FPGA did not initialize.");
+            return Err("Slave FPGA did finish INITialization.");
         }
 
         for i in slice::from_raw_parts(GATEWARE.offset(8), length) {