diff --git a/docs/user/FlowVariables.md b/docs/user/FlowVariables.md
index 56616bcd43..0df148d71d 100644
--- a/docs/user/FlowVariables.md
+++ b/docs/user/FlowVariables.md
@@ -356,6 +356,7 @@ configuration file.
 - [ADDITIONAL_MEMORIES](#ADDITIONAL_MEMORIES)
 - [AUTO_MEMORIES_MACRO_PLACE](#AUTO_MEMORIES_MACRO_PLACE)
 - [AUTO_MEMORIES_REGFILES](#AUTO_MEMORIES_REGFILES)
+- [BLOCKS](#BLOCKS)
 - [CACHED_REPORTS](#CACHED_REPORTS)
 - [CLKGATE_MAP_FILE](#CLKGATE_MAP_FILE)
 - [DFF_LIB_FILE](#DFF_LIB_FILE)
@@ -669,7 +670,6 @@ configuration file.
 - [ADDITIONAL_LEFS](#ADDITIONAL_LEFS)
 - [ADDITIONAL_LIBS](#ADDITIONAL_LIBS)
 - [AUTO_MEMORIES](#AUTO_MEMORIES)
-- [BLOCKS](#BLOCKS)
 - [CAP_MARGIN](#CAP_MARGIN)
 - [CDL_FILES](#CDL_FILES)
 - [CORNER](#CORNER)
diff --git a/flow/scripts/synth_preamble.tcl b/flow/scripts/synth_preamble.tcl
index 6550b0f5ae..f024281f80 100644
--- a/flow/scripts/synth_preamble.tcl
+++ b/flow/scripts/synth_preamble.tcl
@@ -302,6 +302,13 @@ if { [env_var_exists_and_non_empty DONT_USE_CELLS] } {
     lappend lib_dont_use_args -dont_use $cell
   }
 }
+# Never map logic onto a hardened block. A block's timing model gives a
+# constant output a function, and ABC would take the block for a gate.
+if { [env_var_exists_and_non_empty BLOCKS] } {
+  foreach block $::env(BLOCKS) {
+    lappend lib_dont_use_args -dont_use $block
+  }
+}
 
 # Technology mapping for cells
 set abc_args [list -script $abc_script \
diff --git a/flow/scripts/variables.json b/flow/scripts/variables.json
index 0d5e4dedd5..8bebf70c48 100644
--- a/flow/scripts/variables.json
+++ b/flow/scripts/variables.json
@@ -94,7 +94,10 @@
     ]
   },
   "BLOCKS": {
-    "description": "Blocks used as hard macros in a hierarchical flow. Do note that you have to specify block-specific inputs file in the directory mentioned by Makefile.\n"
+    "description": "Blocks used as hard macros in a hierarchical flow. Do note that you have to specify block-specific inputs file in the directory mentioned by Makefile.\n",
+    "stages": [
+      "synth"
+    ]
   },
   "BUFFER_PORTS_ARGS": {
     "description": "Specify arguments to the buffer_ports call during placement. Only used if DONT_BUFFER_PORTS=0.\n",
diff --git a/flow/scripts/variables.yaml b/flow/scripts/variables.yaml
index cd680162d1..ac9d582494 100644
--- a/flow/scripts/variables.yaml
+++ b/flow/scripts/variables.yaml
@@ -1134,6 +1134,8 @@ BLOCKS:
   description: >
     Blocks used as hard macros in a hierarchical flow. Do note that you have to
     specify block-specific inputs file in the directory mentioned by Makefile.
+  stages:
+    - synth
 CDL_FILES:
   description: |
     Insert additional Circuit Description Language (`.cdl`) netlist files.
diff --git a/tools/OpenROAD b/tools/OpenROAD
index f131605002..82a809c749 160000
--- a/tools/OpenROAD
+++ b/tools/OpenROAD
@@ -1 +1 @@
-Subproject commit f131605002c80444f79b18e95e0c7cb657ec024d
+Subproject commit 82a809c74985ed61a7778eb48dc895c5335e462f