diff --git a/software/healthcheck.c b/software/healthcheck.c
index 1f1b7da..be2aefd 100644
--- a/software/healthcheck.c
+++ b/software/healthcheck.c
@@ -279,6 +279,12 @@ void inmClearEntropyLevel(void) {
     inmEntropyLevel = 0;
 }
 
+// Check that the entropy of the last group of bits was high enough for use.
+bool inmEntropyOnTarget(uint32_t entropy, uint32_t numBits) {
+    uint32_t expectedEntropy = numBits*inmExpectedEntropyPerBit;
+    return expectedEntropy < entropy*INM_ACCURACY;
+}
+
 #ifdef TEST_HEALTHCHECK
 
 // Print the tables of statistics.
diff --git a/software/infnoise.c b/software/infnoise.c
index ef2211c..7c3022b 100644
--- a/software/infnoise.c
+++ b/software/infnoise.c
@@ -11,16 +11,17 @@
 // The FT240X has a 512 byte buffer.  Must be multiple of 64
 //#define BUFLEN 512
 #define BUFLEN (64*8)
-#define DESIGN_K 1.736
 #define PREDICTION_BITS 14
 #define LINUX_POOL_SIZE (4096/8)
 
 #ifdef VERSION1
+#define DESIGN_K 1.82
 #define COMP1 2
 #define COMP2 0
 #define SWEN1 4
 #define SWEN2 1
 #else
+#define DESIGN_K 1.736
 #define COMP1 1
 #define COMP2 4
 #define SWEN1 2
@@ -175,7 +176,6 @@ static bool initializeUSB(struct ftdi_context *ftdic, char **message) {
     return true;
 }
 
-
 int main(int argc, char **argv)
 {
     struct ftdi_context ftdic;
@@ -245,7 +245,7 @@ int main(int argc, char **argv)
         }
         uint8_t bytes[BUFLEN/8];
         uint32_t entropy = extractBytes(bytes, inBuf, raw);
-        if(!noOutput && inmHealthCheckOkToUseData()) {
+        if(!noOutput && inmHealthCheckOkToUseData() && inmEntropyOnTarget(entropy, BUFLEN)) {
             processBytes(keccakState, bytes, entropy, raw, writeDevRandom);
         }
     }
diff --git a/software/infnoise.h b/software/infnoise.h
index b3a48fb..364044b 100644
--- a/software/infnoise.h
+++ b/software/infnoise.h
@@ -9,6 +9,7 @@ double inmHealthCheckEstimateK(void);
 double inmHealthCheckEstimateEntropyPerBit(void);
 uint32_t inmGetEntropyLevel(void);
 void inmClearEntropyLevel(void);
+bool inmEntropyOnTarget(uint32_t entropy, uint32_t bits);
 void inmWriteEntropyStart(uint32_t bufLen, bool debug);
 void inmWriteEntropyToPool(uint8_t *bytes, uint32_t length, uint32_t entropy);
 void inmWaitForPoolToHaveRoom(void);