diff --git a/hdl/Makefile b/hdl/Makefile
deleted file mode 100644
index 41ed439..0000000
--- a/hdl/Makefile
+++ /dev/null
@@ -1,4 +0,0 @@
-DOTF=hazard3.f
-TOP=hazard3_alu
-
-include $(SCRIPTS)/formal.mk
diff --git a/hdl/hazard3_config.vh b/hdl/hazard3_config.vh
index 6efac3d..44dc685 100644
--- a/hdl/hazard3_config.vh
+++ b/hdl/hazard3_config.vh
@@ -65,6 +65,9 @@ parameter MARCHID_VAL = 32'h0,
 // Implementation ID for this specific version of Hazard3. Git hash is perfect.
 parameter MIMPID_VAL = 32'h0,
 
+// Each core has a single hardware thread. Multiple cores should have unique IDs.
+parameter MHARTID_VAL = 32'h0,
+
 // ----------------------------------------------------------------------------
 // Performance/size options
 
diff --git a/hdl/hazard3_config_inst.vh b/hdl/hazard3_config_inst.vh
index 0a8d67b..a6ec8a3 100644
--- a/hdl/hazard3_config_inst.vh
+++ b/hdl/hazard3_config_inst.vh
@@ -13,6 +13,7 @@
 .MVENDORID_VAL   (MVENDORID_VAL),
 .MARCHID_VAL     (MARCHID_VAL),
 .MIMPID_VAL      (MIMPID_VAL),
+.MHARTID_VAL     (MHARTID_VAL),
 .REDUCED_BYPASS  (REDUCED_BYPASS),
 .MULDIV_UNROLL   (MULDIV_UNROLL),
 .MUL_FAST        (MUL_FAST),
diff --git a/hdl/hazard3_csr.v b/hdl/hazard3_csr.v
index e5bb895..ba740a5 100644
--- a/hdl/hazard3_csr.v
+++ b/hdl/hazard3_csr.v
@@ -506,8 +506,7 @@ always @ (*) begin
 	end
 	MHARTID: if (CSR_M_MANDATORY) begin
 		decode_match = !wen_soon; // MRO
-		// There is only one hart, and spec says this must be numbered 0.
-		rdata = {XLEN{1'b0}};
+		rdata = MHARTID_VAL;
 	end
 
 	MSTATUS: if (CSR_M_MANDATORY || CSR_M_TRAP) begin