diff --git a/common/util.h b/common/util.h
new file mode 100644
index 00000000..2313a290
--- /dev/null
+++ b/common/util.h
@@ -0,0 +1,63 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  David Shah <david@symbioticeda.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <string>
+#include "nextpnr.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+// Get a value from a map-style container, returning default if value is not
+// found
+template<typename Container, typename KeyType, typename ValueType>
+ValueType get_or_default(const Container &ct, const KeyType &key,
+                         ValueType def = ValueType())
+{
+    auto found = ct.find(key);
+    if (found == ct.end())
+        return def;
+    else
+        return found->second;
+};
+
+// Get a value from a map-style container, converting to int, and returning
+// default if value is not found
+template<typename Container, typename KeyType>
+int int_or_default(const Container &ct, const KeyType &key,
+                         int def = 0)
+{
+    auto found = ct.find(key);
+    if (found == ct.end())
+        return def;
+    else
+        return std::stoi(found->second);
+};
+
+// As above, but convert to bool
+template<typename Container, typename KeyType>
+bool bool_or_default(const Container &ct, const KeyType &key,
+                   bool def = false)
+{
+    return bool(int_or_default(ct, key, int(def)));
+};
+NEXTPNR_NAMESPACE_END
+
+#endif
diff --git a/ice40/arch_place.cc b/ice40/arch_place.cc
index 93b7beb4..83dd63aa 100644
--- a/ice40/arch_place.cc
+++ b/ice40/arch_place.cc
@@ -19,6 +19,7 @@
 
 #include "arch_place.h"
 #include "cells.h"
+#include "util.h"
 
 NEXTPNR_NAMESPACE_BEGIN
 
@@ -39,7 +40,7 @@ static bool logicCellsCompatible(const std::vector<const CellInfo *> &cells)
     std::unordered_set<const NetInfo *> locals;
 
     for (auto cell : cells) {
-        if (std::stoi(cell->params.at("DFF_ENABLE"))) {
+        if (bool_or_default(cell->params, "DFF_ENABLE")) {
             if (!dffs_exist) {
                 dffs_exist = true;
                 cen = get_net_or_nullptr(cell, "CEN");
@@ -53,7 +54,7 @@ static bool logicCellsCompatible(const std::vector<const CellInfo *> &cells)
                 if (!is_global_net(sr))
                     locals.insert(sr);
 
-                if (std::stoi(cell->params.at("NEG_CLK"))) {
+                if (bool_or_default(cell->params, "NEG_CLK")) {
                     dffs_neg = true;
                 }
             } else {
@@ -63,7 +64,7 @@ static bool logicCellsCompatible(const std::vector<const CellInfo *> &cells)
                     return false;
                 if (sr != get_net_or_nullptr(cell, "SR"))
                     return false;
-                if (dffs_neg != bool(std::stoi(cell->params.at("NEG_CLK"))))
+                if (dffs_neg != bool_or_default(cell->params, "NEG_CLK"))
                     return false;
             }
         }