diff --git a/common/placer1.cc b/common/placer1.cc
index 837010fe..5171af19 100644
--- a/common/placer1.cc
+++ b/common/placer1.cc
@@ -42,6 +42,7 @@
 #include "fast_bels.h"
 #include "log.h"
 #include "place_common.h"
+#include "scope_lock.h"
 #include "timing.h"
 #include "util.h"
 
@@ -142,7 +143,8 @@ class SAPlacer
     bool place(bool refine = false)
     {
         log_break();
-        ctx->lock();
+
+        nextpnr::ScopeLock<Context> lock(ctx);
 
         size_t placed_cells = 0;
         std::vector<CellInfo *> autoplaced;
@@ -421,7 +423,7 @@ class SAPlacer
                 log_error("constraint satisfaction check failed for cell '%s' at Bel '%s'\n", cell.first.c_str(ctx),
                           ctx->nameOfBel(cell.second->bel));
         timing_analysis(ctx);
-        ctx->unlock();
+
         return true;
     }
 
@@ -1251,9 +1253,10 @@ bool placer1(Context *ctx, Placer1Cfg cfg)
         return true;
     } catch (log_execution_error_exception) {
 #ifndef NDEBUG
+        ctx->lock();
         ctx->check();
-#endif
         ctx->unlock();
+#endif
         return false;
     }
 }
@@ -1272,9 +1275,10 @@ bool placer1_refine(Context *ctx, Placer1Cfg cfg)
         return true;
     } catch (log_execution_error_exception) {
 #ifndef NDEBUG
+        ctx->lock();
         ctx->check();
-#endif
         ctx->unlock();
+#endif
         return false;
     }
 }
diff --git a/common/placer_heap.cc b/common/placer_heap.cc
index cea862af..eb931a37 100644
--- a/common/placer_heap.cc
+++ b/common/placer_heap.cc
@@ -331,8 +331,6 @@ class HeAPPlacer
             return false;
         }
 
-        lock.unlock_early();
-
         auto endtt = std::chrono::high_resolution_clock::now();
         log_info("HeAP Placer Time: %.02fs\n", std::chrono::duration<double>(endtt - startt).count());
         log_info("  of which solving equations: %.02fs\n", solve_time);
@@ -340,6 +338,7 @@ class HeAPPlacer
         log_info("  of which strict legalisation: %.02fs\n", sl_time);
 
         ctx->check();
+        lock.unlock_early();
 
         if (!placer1_refine(ctx, Placer1Cfg(ctx))) {
             return false;
diff --git a/common/router1.cc b/common/router1.cc
index efc06b06..bffbc9f9 100644
--- a/common/router1.cc
+++ b/common/router1.cc
@@ -23,6 +23,7 @@
 
 #include "log.h"
 #include "router1.h"
+#include "scope_lock.h"
 #include "timing.h"
 
 namespace {
@@ -805,7 +806,7 @@ bool router1(Context *ctx, const Router1Cfg &cfg)
     try {
         log_break();
         log_info("Routing..\n");
-        ctx->lock();
+        nextpnr::ScopeLock<Context> lock(ctx);
         auto rstart = std::chrono::high_resolution_clock::now();
 
         log_info("Setting up routing queue.\n");
@@ -854,7 +855,6 @@ bool router1(Context *ctx, const Router1Cfg &cfg)
                 router.check();
                 ctx->check();
 #endif
-                ctx->unlock();
                 return false;
             }
         }
@@ -878,13 +878,13 @@ bool router1(Context *ctx, const Router1Cfg &cfg)
         timing_analysis(ctx, true /* slack_histogram */, true /* print_fmax */, true /* print_path */,
                         true /* warn_on_failure */);
 
-        ctx->unlock();
         return true;
     } catch (log_execution_error_exception) {
 #ifndef NDEBUG
+        ctx->lock();
         ctx->check();
-#endif
         ctx->unlock();
+#endif
         return false;
     }
 }
diff --git a/common/router2.cc b/common/router2.cc
index abe5f302..1b7a6fed 100644
--- a/common/router2.cc
+++ b/common/router2.cc
@@ -36,6 +36,7 @@
 #include "log.h"
 #include "nextpnr.h"
 #include "router1.h"
+#include "scope_lock.h"
 #include "timing.h"
 #include "util.h"
 
@@ -1161,6 +1162,8 @@ struct Router2
         ThreadContext st;
         int iter = 1;
 
+        nextpnr::ScopeLock<Context> lock(ctx);
+
         for (size_t i = 0; i < nets_by_udata.size(); i++)
             route_queue.push_back(i);
 
@@ -1237,6 +1240,8 @@ struct Router2
 
         log_info("Running router1 to check that route is legal...\n");
 
+        lock.unlock_early();
+
         router1(ctx, Router1Cfg(ctx));
     }
 };