diff --git a/ChangeLog b/ChangeLog
index 3d8e10434..93741fb43 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -37,6 +37,12 @@ Changes in version 0.2.0.33 - 200?-??-??
     - Fix another case of assuming, when a specific exit is requested,
       that we know more than the user about what hosts it allows.
       Fixes one case of bug 752.  Patch from rovv.
+    - Clip the MaxCircuitDirtiness config option to a minimum of 10
+      seconds. Warn the user if lower values are given in the
+      configuration. Bugfix on 0.1.0.1-rc. Patch by Sebastian.
+    - Clip the CircuitBuildTimeout to a minimum of 30 seconds. Warn the
+      user if lower values are given in the configuration. Bugfix on
+      0.1.1.17-rc. Patch by Sebastian.
 
   o Minor features:
     - Report the case where all signatures in a detached set are rejected
diff --git a/src/or/config.c b/src/or/config.c
index d69254b30..3e6cac869 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -2681,6 +2681,15 @@ compute_publishserverdescriptor(or_options_t *options)
 /** Highest allowable value for RendPostPeriod. */
 #define MAX_DIR_PERIOD (MIN_ONION_KEY_LIFETIME/2)
 
+/** Lowest allowable value for CircuitBuildTimeout; values too low will
+ * increase network load because of failing connections being retried, and
+ * might prevent users from connecting to the network at all. */
+#define MIN_CIRCUIT_BUILD_TIMEOUT 30
+
+/** Lowest allowable value for MaxCircuitDirtiness; if this is too low, Tor
+ * will generate too many circuits and potentially overload the network. */
+#define MIN_MAX_CIRCUIT_DIRTINESS 10
+
 /** Return 0 if every setting in <b>options</b> is reasonable, and a
  * permissible transition from <b>old_options</b>. Else return -1.
  * Should have no side effects, except for normalizing the contents of
@@ -3084,6 +3093,18 @@ options_validate(or_options_t *old_options, or_options_t *options,
     options->RendPostPeriod = MAX_DIR_PERIOD;
   }
 
+  if (options->CircuitBuildTimeout < MIN_CIRCUIT_BUILD_TIMEOUT) {
+    log(LOG_WARN, LD_CONFIG, "CircuitBuildTimeout option is too short; "
+      "raising to %d seconds.", MIN_CIRCUIT_BUILD_TIMEOUT);
+    options->CircuitBuildTimeout = MIN_CIRCUIT_BUILD_TIMEOUT;
+  }
+
+  if (options->MaxCircuitDirtiness < MIN_MAX_CIRCUIT_DIRTINESS) {
+    log(LOG_WARN, LD_CONFIG, "MaxCircuitDirtiness option is too short; "
+      "raising to %d seconds.", MIN_MAX_CIRCUIT_DIRTINESS);
+    options->MaxCircuitDirtiness = MIN_MAX_CIRCUIT_DIRTINESS;
+  }
+
   if (options->KeepalivePeriod < 1)
     REJECT("KeepalivePeriod option must be positive.");