diff --git a/dv/uvm/icache/dv/ibex_icache_core_agent/ibex_icache_core_driver.sv b/dv/uvm/icache/dv/ibex_icache_core_agent/ibex_icache_core_driver.sv
index 689145ff..cfbd5a7f 100644
--- a/dv/uvm/icache/dv/ibex_icache_core_agent/ibex_icache_core_driver.sv
+++ b/dv/uvm/icache/dv/ibex_icache_core_agent/ibex_icache_core_driver.sv
@@ -59,12 +59,24 @@ class ibex_icache_core_driver
     // Drive the enable state
     cfg.vif.driver_cb.enable <= req.enable;
 
+    // Branch, invalidate and set new seed immediately. When the branch has finished, read num_insns
+    // instructions and wiggle the branch_spec line until everything is done.
     fork
+      begin
         cfg.vif.branch_to(req.branch_addr);
-        if (req.invalidate) invalidate();
-        if (req.new_seed != 0) drive_new_seed(req.new_seed);
-        read_insns(rsp, req.num_insns);
+        fork
+          read_insns(rsp, req.num_insns);
+          drive_branch_spec();
+        join_any
+      end
+      if (req.invalidate) invalidate();
+      if (req.new_seed != 0) drive_new_seed(req.new_seed);
     join
+
+    // Kill the drive_branch_spec process and reset branch_spec if necessary.
+    disable fork;
+    cfg.vif.driver_cb.branch_spec <= 0;
+
   endtask
 
   // Drive the cache for a "req transaction".
@@ -89,12 +101,23 @@ class ibex_icache_core_driver
     // Drive the enable state
     cfg.vif.driver_cb.enable <= req.enable;
 
+    // Lower req, invalidate and set new seed immediately. After req_low_cycles cycles, start
+    // reading instructions. Wiggle the branch_spec line the whole time.
     fork
-        if (req_low_cycles > 0) lower_req(req_low_cycles);
-        if (req.invalidate) invalidate();
-        if (req.new_seed != 0) drive_new_seed(req.new_seed);
-    join
-    read_insns(rsp, req.num_insns);
+      begin
+        fork
+          if (req_low_cycles > 0) lower_req(req_low_cycles);
+          if (req.invalidate) invalidate();
+          if (req.new_seed != 0) drive_new_seed(req.new_seed);
+        join
+        read_insns(rsp, req.num_insns);
+      end
+      drive_branch_spec();
+    join_any
+
+    // Kill the drive_branch_spec process and reset branch_spec if necessary.
+    disable fork;
+    cfg.vif.driver_cb.branch_spec <= 0;
   endtask
 
   // Read up to num_insns instructions from the cache, stopping early on an error. If there was an
@@ -110,6 +133,14 @@ class ibex_icache_core_driver
     end
   endtask
 
+  // Randomly drive the branch_spec line one cycle in 64. Never returns.
+  task automatic drive_branch_spec();
+    forever begin
+      cfg.vif.driver_cb.branch_spec <= $urandom_range(64) == 0;
+      @(cfg.vif.driver_cb);
+    end
+  endtask
+
   // Read a single instruction from the cache
   virtual task automatic read_insn();
     int unsigned delay;