diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 9a75a430be..0c047338cd 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -49,9 +49,8 @@ using node::UpdateTime;
 
 /**
  * Return average network hashes per second based on the last 'lookup' blocks,
- * or from the last difficulty change if 'lookup' is -1.
- * If 'height' is -1, compute the estimate from current chain tip.
- * If 'height' is a valid block height, compute the estimate at the time when a given block was found.
+ * or from the last difficulty change if 'lookup' is nonpositive.
+ * If 'height' is nonnegative, compute the estimate at the time when a given block was found.
  */
 static UniValue GetNetworkHashPS(int lookup, int height, const CChain& active_chain) {
     if (lookup < -1 || lookup == 0) {
@@ -64,7 +63,7 @@ static UniValue GetNetworkHashPS(int lookup, int height, const CChain& active_ch
 
     const CBlockIndex* pb = active_chain.Tip();
 
-    if (height >= 0) {
+    if (height >= 0 && height < active_chain.Height()) {
         pb = active_chain[height];
     }
 
@@ -72,7 +71,7 @@ static UniValue GetNetworkHashPS(int lookup, int height, const CChain& active_ch
         return 0;
 
     // If lookup is -1, then use blocks since last difficulty change.
-    if (lookup == -1)
+    if (lookup <= 0)
         lookup = pb->nHeight % Params().GetConsensus().DifficultyAdjustmentInterval() + 1;
 
     // If lookup is larger than chain, then set it to chain length.
diff --git a/test/functional/rpc_blockchain.py b/test/functional/rpc_blockchain.py
index f3f1104862..d5885f1ab4 100755
--- a/test/functional/rpc_blockchain.py
+++ b/test/functional/rpc_blockchain.py
@@ -437,6 +437,7 @@ class BlockchainTest(BitcoinTestFramework):
 
     def _test_getnetworkhashps(self):
         self.log.info("Test getnetworkhashps")
+        hashes_per_second = self.nodes[0].getnetworkhashps()
         assert_raises_rpc_error(
             -3,
             textwrap.dedent("""
@@ -448,6 +449,9 @@ class BlockchainTest(BitcoinTestFramework):
             """).strip(),
             lambda: self.nodes[0].getnetworkhashps("a", []),
         )
+        # This should be 2 hashes every 10 minutes or 1/300
+        assert abs(hashes_per_second * 300 - 1) < 0.0001
+
         assert_raises_rpc_error(
             -8,
             "Block does not exist at specified height",
@@ -473,10 +477,6 @@ class BlockchainTest(BitcoinTestFramework):
         hashes_per_second = self.nodes[0].getnetworkhashps(100, 0)
         assert_equal(hashes_per_second, 0)
 
-        # This should be 2 hashes every 10 minutes or 1/300
-        hashes_per_second = self.nodes[0].getnetworkhashps()
-        assert abs(hashes_per_second * 300 - 1) < 0.0001
-
         # Ensure long lookups get truncated to chain length
         hashes_per_second = self.nodes[0].getnetworkhashps(self.nodes[0].getblockcount() + 1000)
         assert hashes_per_second > 0.003