diff --git a/README.md b/README.md
index 263cd0f7..047b8271 100644
--- a/README.md
+++ b/README.md
@@ -365,6 +365,10 @@ methods, here are some links:
 
 ## Version history##
 
+### version 2.2.1 ###
+
+**swarm** 2.2.1 fixes a memory allocation bug for d=1.
+
 ### version 2.2.0 ###
 
 **swarm** 2.2.0 fixes several problems and improves usability.
diff --git a/man/swarm.1 b/man/swarm.1
index 150b7049..a5114549 100644
--- a/man/swarm.1
+++ b/man/swarm.1
@@ -1,5 +1,5 @@
 .\" ============================================================================
-.TH swarm 1 "October 17, 2017" "version 2.2.0" "USER COMMANDS"
+.TH swarm 1 "October 27, 2017" "version 2.2.1" "USER COMMANDS"
 .\" ============================================================================
 .SH NAME
 swarm \(em find clusters of nearly-identical nucleotide amplicons
@@ -389,6 +389,9 @@ New features and important modifications of \fBswarm\fR (short lived
 or minor bug releases are not mentioned):
 .RS
 .TP
+.BR v2.2.1\~ "released October 27, 2017"
+Version 2.2.1 fixes a memory allocation bug for d=1.
+.TP
 .BR v2.2.0\~ "released October 17, 2017"
 Version 2.2.0 fixes several problems and improves usability. Corrected
 output to structure and uclust files when using fastidious
diff --git a/man/swarm_manual.pdf b/man/swarm_manual.pdf
index 79308527..0d5392a1 100644
Binary files a/man/swarm_manual.pdf and b/man/swarm_manual.pdf differ
diff --git a/src/algod1.cc b/src/algod1.cc
index 4971df32..728059a3 100644
--- a/src/algod1.cc
+++ b/src/algod1.cc
@@ -491,7 +491,8 @@ void process_seed(int subseed)
     {
       if (global_hits_count + ti[t].hits_count > global_hits_alloc)
         {
-          global_hits_alloc <<= 1;
+          while (global_hits_count + ti[t].hits_count > global_hits_alloc)
+            global_hits_alloc <<= 1;
           global_hits_data = (int*)xrealloc(global_hits_data,
                                             global_hits_alloc * sizeof(int));
         }
diff --git a/src/swarm.h b/src/swarm.h
index 82cdffcb..7b831739 100644
--- a/src/swarm.h
+++ b/src/swarm.h
@@ -54,7 +54,7 @@
 #define LINE_MAX 2048
 #endif
 
-#define SWARM_VERSION "2.2.0"
+#define SWARM_VERSION "2.2.1"
 #define WIDTH 32
 #define WIDTH_SHIFT 5
 #define BLOCKWIDTH 32