diff --git a/CHANGELOG.md b/CHANGELOG.md
index f38cc8ff5..4f1a127a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased (4.0.1)]
 
+### Fixed
+
+- **Breaking**: The 4.0.0 change replacing the `Agiodisc_t` struct member
+  `putstr` by `printf` has been reverted
+
 ## [4.0.0] – 2022-05-29
 
 ### Changed
diff --git a/cmd/gvpr/gvprmain.c b/cmd/gvpr/gvprmain.c
index 188cfdf94..92872f8cd 100644
--- a/cmd/gvpr/gvprmain.c
+++ b/cmd/gvpr/gvprmain.c
@@ -47,14 +47,17 @@ static int iofread(void *chan, char *buf, int bufsize)
   return (int)fread(buf, 1, (size_t)bufsize, chan);
 }
 
+static int ioputstr(void *chan, const char *str)
+{
+  return fputs(str, chan);
+}
+
 static int ioflush(void *chan)
 {
   return fflush(chan);
 }
 
-typedef int (*printfn)(void *chan, const char *format, ...);
-
-static Agiodisc_t gprIoDisc = { iofread, (printfn)fprintf, ioflush };
+static Agiodisc_t gprIoDisc = { iofread, ioputstr, ioflush };
 
 static Agdisc_t gprDisc = { &AgMemDisc, &AgIdDisc, &gprIoDisc };
 
diff --git a/lib/cgraph/cgraph.3 b/lib/cgraph/cgraph.3
index ed7392c06..67e35c2e9 100644
--- a/lib/cgraph/cgraph.3
+++ b/lib/cgraph/cgraph.3
@@ -487,14 +487,14 @@ The I/O discipline provides an abstraction for the reading and writing of graphs
 .P0
 struct Agiodisc_s {
     int        (*fread)(void *chan, char *buf, int bufsize);
-    int        (*printf)(void *chan, const char *format, ...);
+    int        (*putstr)(void *chan, char *str);
     int        (*flush)(void *chan);    /* sync */
 } ;
 .P1
 Normally, the \fBFILE\fP structure and its related functions are used for I/O. At times, though,
 an application may need to use a totally different type of character source. The associated
 state or stream information is provided by the \fIchan\fP argument to \fBagread\fP or \fBagwrite\fP.
-The discipline function \fIfread\fP and \fIprintf\fP provide the corresponding functions for
+The discipline function \fIfread\fP and \fIputstr\fP provide the corresponding functions for
 read and writing.
 
 .SH "MEMORY DISCIPLINE"
diff --git a/lib/cgraph/cgraph.h b/lib/cgraph/cgraph.h
index 7b005c442..cbec3bbe6 100644
--- a/lib/cgraph/cgraph.h
+++ b/lib/cgraph/cgraph.h
@@ -169,7 +169,7 @@ struct Agiddisc_s {		/* object ID allocator */
 
 struct Agiodisc_s {
     int (*afread) (void *chan, char *buf, int bufsize);
-    int (*printf)(void *chan, const char *format, ...);
+    int (*putstr) (void *chan, const char *str);
     int (*flush) (void *chan);	/* sync */
     /* error messages? */
 };
diff --git a/lib/cgraph/io.c b/lib/cgraph/io.c
index d8b136804..66c605ae6 100644
--- a/lib/cgraph/io.c
+++ b/lib/cgraph/io.c
@@ -24,15 +24,17 @@ static int iofread(void *chan, char *buf, int bufsize)
 }
 
 /* default IO methods */
+static int ioputstr(void *chan, const char *str)
+{
+    return fputs(str, chan);
+}
 
 static int ioflush(void *chan)
 {
     return fflush(chan);
 }
 
-typedef int (*printfn)(void *chan, const char *format, ...);
-
-Agiodisc_t AgIoDisc = { iofread, (printfn)fprintf, ioflush };
+Agiodisc_t AgIoDisc = { iofread, ioputstr, ioflush };
 
 typedef struct {
     const char *data;
@@ -78,7 +80,7 @@ static Agraph_t *agmemread0(Agraph_t *arg_g, const char *cp)
     rdr_t rdr;
     Agdisc_t disc;
 
-    memIoDisc.printf = AgIoDisc.printf;
+    memIoDisc.putstr = AgIoDisc.putstr;
     memIoDisc.flush = AgIoDisc.flush;
     rdr.data = cp;
     rdr.len = strlen(cp);
diff --git a/lib/cgraph/write.c b/lib/cgraph/write.c
index e14f7d835..9e72d2c5c 100644
--- a/lib/cgraph/write.c
+++ b/lib/cgraph/write.c
@@ -26,7 +26,7 @@ typedef void iochan_t;
 
 static int ioput(Agraph_t * g, iochan_t * ofile, char *str)
 {
-    return AGDISC(g, io)->printf(ofile, "%s", str);
+    return AGDISC(g, io)->putstr(ofile, str);
 
 }
 
diff --git a/lib/gvpr/compile.c b/lib/gvpr/compile.c
index a7fe27bf5..3704f51d9 100644
--- a/lib/gvpr/compile.c
+++ b/lib/gvpr/compile.c
@@ -66,14 +66,17 @@ static int iofread(void *chan, char *buf, int bufsize)
     return (int)read(sffileno(chan), buf, bufsize);
 }
 
+static int ioputstr(void *chan, const char *str)
+{
+    return sfputr(chan, str, -1);
+}
+
 static int ioflush(void *chan)
 {
     return sfsync(chan);
 }
 
-typedef int (*printfn)(void *chan, const char *format, ...);
-
-static Agiodisc_t gprIoDisc = { iofread, (printfn)sfprintf, ioflush };
+static Agiodisc_t gprIoDisc = { iofread, ioputstr, ioflush };
 
 #ifdef GVDLL
 static Agdisc_t gprDisc = { 0, 0, &gprIoDisc };
diff --git a/plugin/core/gvrender_core_dot.c b/plugin/core/gvrender_core_dot.c
index c45563460..63eb5e535 100644
--- a/plugin/core/gvrender_core_dot.c
+++ b/plugin/core/gvrender_core_dot.c
@@ -511,7 +511,7 @@ static void xdot_end_graph(graph_t* g)
     textflags[EMIT_GLABEL] = 0;
 }
 
-typedef int (*printfn)(void *chan, const char *format, ...);
+typedef int (*putstrfn) (void *chan, const char *str);
 typedef int (*flushfn) (void *chan);
 static void dot_end_graph(GVJ_t *job)
 {
@@ -521,7 +521,7 @@ static void dot_end_graph(GVJ_t *job)
 
     if (io.afread == NULL) {
 	io.afread = AgIoDisc.afread;
-	io.printf = (printfn)gvprintf;
+	io.putstr = (putstrfn)gvputs;
 	io.flush = (flushfn)gvflush;
     }
 
diff --git a/plugin/core/gvrender_core_json.c b/plugin/core/gvrender_core_json.c
index bab5d64af..88715a93a 100644
--- a/plugin/core/gvrender_core_json.c
+++ b/plugin/core/gvrender_core_json.c
@@ -693,7 +693,7 @@ static void write_graph(Agraph_t * g, GVJ_t * job, int top, state_t* sp)
 	gvputs(job, "}");
 }
 
-typedef int (*printfn)(void *chan, const char *format, ...);
+typedef int (*putstrfn) (void *chan, const char *str);
 typedef int (*flushfn) (void *chan);
 
 static void json_end_graph(GVJ_t *job)
@@ -704,7 +704,7 @@ static void json_end_graph(GVJ_t *job)
 
     if (io.afread == NULL) {
 	io.afread = AgIoDisc.afread;
-	io.printf = (printfn)gvprintf;
+	io.putstr = (putstrfn)gvputs;
 	io.flush = (flushfn)gvflush;
     }
 
diff --git a/tclpkg/tcldot/tcldot.c b/tclpkg/tcldot/tcldot.c
index 335d8e469..b747124cf 100644
--- a/tclpkg/tcldot/tcldot.c
+++ b/tclpkg/tcldot/tcldot.c
@@ -163,7 +163,7 @@ int Tcldot_Init(Tcl_Interp * interp)
     /* build disciplines dynamically so we can selectively replace functions */
 
     ictx->myioDisc.afread = NULL;            /* set in dotread() or dotstring() according to need */
-    ictx->myioDisc.printf = AgIoDisc.printf; /* no change */
+    ictx->myioDisc.putstr = AgIoDisc.putstr; /* no change */
     ictx->myioDisc.flush = AgIoDisc.flush;   /* no change */
 
     ictx->mydisc.mem = &AgMemDisc;           /* no change */
diff --git a/lib/common/output.c b/lib/common/output.c
index c91dfe41e..648409c5a 100644
--- a/lib/common/output.c
+++ b/lib/common/output.c
@@ -80,11 +80,11 @@ void write_plain(GVJ_t *job, graph_t *g,
     bezier bz;
     pointf pt;
     char *lbl;
     char* fillcolor;
 
-    print = g->clos->disc.io->printf;
+    print = g->clos->disc.io->putstr;
 //    setup_graph(job, g);
     setYInvert(g);
     pt = GD_bb(g).UR;
     print(f, "graph %.5g %.5g %.5g\n", job->zoom, PS2INCH(pt.x), PS2INCH(pt.y));
     for (n = agfstnode(g); n; n = agnxtnode(g, n)) {